Disc therapy

ABSTRACT

Apparatus is provided for treating an intervertebral disc of a subject, the apparatus including: at least one intra-pulposus exposed electrode surface, which is configured to be implanted in a nucleus pulposus of the intervertebral disc; and one or more extra-pulposus exposed electrode surfaces, which are configured to be implanted outside the nucleus pulposus, in electrical communication with the intervertebral disc. Control circuitry is electrically coupled to the at least one intra-pulposus exposed electrode surface and one or more extra-pulposus exposed electrode surfaces. The control circuitry is configured to drive fluid and introduce nutritional substances into the intervertebral disc, by applying a voltage between the at least one intra-pulposus exposed electrode surface and the one or more extra-pulposus exposed electrode surfaces. Other embodiments are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is:

(a) a continuation of U.S. application Ser. No. 16/332,606, filed Mar.12, 2019, which is the U.S. national stage of International ApplicationPCT/IL2017/051032, filed Sep. 13, 2017, which is a continuation of U.S.application Ser. No. 15/263,910, filed Sep. 13, 2016, now U.S. Pat. No.9,950,156, and

(b) a continuation-in-part of U.S. application Ser. No. 16/695,936,filed Nov. 26, 2019, which is a continuation of U.S. application Ser.No. 16/064,604, filed Jun. 21, 2018, now U.S. Pat. No. 10,518,085, whichis the US National Stage of International Application PCT/IL2016/051363,filed Dec. 21, 2016, which is a continuation of U.S. application Ser.No. 14/982,187, filed Dec. 29, 2015, now U.S. Pat. No. 9,770,591.

All of the above-mentioned applications are assigned to the assignee ofthe present application and are incorporated herein by reference.

FIELD OF THE APPLICATION

The present invention relates generally to therapeutic electricaltechniques.

BACKGROUND OF THE APPLICATION

The intervertebral discs form cartilaginous joints between the endplates of vertebrae to provide shock absorption. The discs include twomain regions: the nucleus pulposus, which is an inner, soft and highlyhydrated structure, and the annulus fibrosus, which is a strongstructure including lamellae (concentric sheets of collagen fibers),which surrounds the nucleus. The three major constituents of the discsare water, fibrillar collagens, and aggrecan. The proportion of thesecomponents varies across the disc, with the nucleus having a higherconcentration of aggrecan and water and a lower collagen content thanother regions of the disc. The loss of water content, particularly inthe nucleus pulposus, is associated with disc degeneration, and with adecrease in disc height and abnormal loading of other spinal structures.

U.S. Pat. No. 8,577,469 to Gross, which is assigned to the assignee ofthe present application and is incorporated herein by reference,describes apparatus for treating an intervertebral disc of a subject.The apparatus includes a first electrode, configured to be inserted intoa nucleus pulposus of the disc, and a second electrode, configured to beplaced outside of the nucleus pulposus, in a vicinity of the nucleuspulposus. A control unit is configured to drive a current between thefirst and second electrodes, and to configure the current toelectroosmotically drive fluid between inside and outside the nucleuspulposus. Other embodiments are also described

US Patent Application Publication 2005/0277996 to Podhajsky describes amethod for reducing intervertebral pressure, including providing anelectrode, having proximal and distal ends, and a generator, which isoperatively connected to the proximal end of the electrode, and isconfigured to supply radiofrequency current thereto. The method alsoincludes inserting at least a portion of the distal end of the electrodeinto the nucleus pulposus of an intervertebral disc and activating thegenerator to heat the nucleus pulposus. The electrode may be insertedinto the intervertebral disc through its first lateral side and/or itssecond lateral side, and may be substantially parallel to the major orminor axis of the nucleus pulposus.

SUMMARY OF THE APPLICATION

In some embodiments of the present invention, anintervertebral-disc-treatment system is provided for treating anintervertebral disc of a subject. The intervertebral-disc-treatmentsystem comprises (a) an electrode, which is configured to be implantedpartially within a nucleus pulposus of the disc, and (b) one or moreextra-pulposus exposed electrode surfaces, which are configured to beimplanted outside the nucleus pulposus, in electrical communication withthe disc, in a vicinity of an external surface of an annulus fibrosus ofthe disc. The intervertebral-disc-treatment system further comprisesimplantable or external control circuitry, which is typicallyelectrically coupled, by one or more electrode leads, to the exposedelectrode surfaces and the electrode.

For some applications, the electrode comprises a wire, which typicallyhas a wire diameter of between 50 and 150 microns, such as 100 microns.The wire includes:

-   -   a non-electrically-insulated current-application longitudinal        segment, which, in the absence of any applied forces, is        helically coiled and typically has (a) a mean pitch of between        1.1 and 2 times the wire diameter, and (b) an entire        longitudinal length of between 5 and 35 mm, and    -   an electrically-insulated lead longitudinal segment, which        typically has an entire longitudinal length of between 5 and 80        mm, in the absence of any applied forces.

For some applications, the current-application longitudinal segment hasan outer coil diameter of between 3 and 7 times the wire diameter, inthe absence of any applied forces.

Typically, because of the above-mentioned dimensions, including thepitch, the current-application longitudinal segment is highly flexible(both in its ability to bend and its ability to longitudinally stretchand contract), which reduces the application of forces on theintervertebral disc, and thus generally causes no or less trauma to theintervertebral disc, including the nucleus pulposus, than a more rigidelectrode might cause, particularly over time during repeated motion ofthe disc.

For some applications, the lead longitudinal segment is coiled, in theabsence of any applied forces. For some applications, the leadlongitudinal segment has one or more of the following dimensions, in theabsence of any applied forces: (a) a mean pitch that is greater than themean pitch P₁ of the current-application longitudinal segment, (b) amean pitch of between 2 and 3 times the wire diameter, (c) an outer coildiameter that equals between 90% and 110% of the outer coil diameter ofthe current-application longitudinal segment, and/or (d) an outer coildiameter of between 3 and 7 times the wire diameter. Typically,providing the above-mentioned pitches enables the thorough applicationof insulation to the electrically-insulated lead longitudinal segment,particularly if a vapor deposition process is used to apply theinsulation (e.g., parylene). In addition, the lead longitudinal segmentmay have a greater pitch than the current-application longitudinalsegment in part because the lead longitudinal segment generally does notrequire as much flexibility as the current-application longitudinalsegment.

For some applications, the wire further includes an the intermediatelongitudinal segment, which (a) is longitudinally between thecurrent-application longitudinal segment and the lead longitudinalsegment, (b) typically has an entire longitudinal length of between 1and 6 mm, in the absence of any applied forces, and (c) in the absenceof any applied forces, either (i) is coiled, and has a mean pitchgreater than the outer coil diameter of the current-applicationlongitudinal segment, or (ii) is not coiled. For some applications, theintermediate longitudinal segment is electrically insulated along atleast a longitudinal portion of the intermediate longitudinal segment.For some applications in which the intermediate longitudinal segment iscoiled, the intermediate longitudinal segment has one or more of thefollowing dimensions, in the absence of any applied forces: (a) a meanpitch of between 125% and 250% of the outer coil diameter of thecurrent-application longitudinal segment, (b) a mean pitch of between 5and 20 times the wire diameter, (c) a mean pitch P₃ that equals (i) atleast the mean pitch of the current-application longitudinal segment,and (ii) no more than the mean pitch of the lead longitudinal segment,(d) an outer coil diameter equal to between 90% and 110% of the outercoil diameter of the current-application longitudinal segment, and/or(e) an outer coil diameter of between 3 and 7 times the wire diameter.

For some applications, the wire further includes a pin-connectorlongitudinal segment. The lead longitudinal segment is longitudinallybetween the current-application longitudinal segment and thepin-connector longitudinal segment. For these applications, theintervertebral-disc-treatment system typically comprises an electrodeassembly, which comprises the electrode and a pin, which is mechanicallyfixed to and in electrical communication with the pin-connectorlongitudinal segment. Typically, the area surrounding the pin and thepin-connector longitudinal segment is electrically insulated, such as bysilicone.

At least a portion of the electrode is implanted in a body of a subject,typically such that:

-   -   the current-application longitudinal segment is disposed at        least partially in the intervertebral disc of the subject,        typically entirely in the intervertebral disc (either entirely        in the nucleus pulposus of the intervertebral disc, or partially        in a nucleus pulposus of the intervertebral disc and partially        in the annulus fibrosus of the intervertebral disc),    -   at least a portion of the lead longitudinal segment is disposed        in the body of the subject outside the intervertebral disc, and    -   if provided, the intermediate longitudinal segment is disposed        at least in part in the annulus fibrosus of the intervertebral        disc; providing the relatively large pitch for the intermediate        longitudinal segment, or not coiling the intermediate        longitudinal segment, may reduce the likelihood that the portion        of the intermediate longitudinal segment that is within the        annulus fibrosus forms a tunnel, which might cause leakage of        fluid from the nucleus pulposus.

In some applications of the present invention, a method of implanting atleast a portion of an electrode in a body of a subject is provided, themethod comprising:

-   -   inserting a hollow insertion needle into an intervertebral disc        of the subject;    -   aligning an electrode loader with the hollow insertion needle,        while the electrode is preloaded in a hollow loader needle of        the electrode loader, and a loader stylet of the electrode        loader is preloaded partially in the hollow loader needle and        disposed such a distal end of the loader stylet abuts a proximal        end of the electrode;    -   connecting the electrode loader to the hollow insertion needle,        such that a distal end of the hollow loader needle abuts a        proximal end of the hollow insertion needle;    -   advancing the electrode into the hollow insertion needle by        advancing the loader stylet distally within the hollow loader        needle so that the loader stylet pushes the electrode distally        from the hollow loader needle into the insertion needle;    -   aligning a needle-withdrawal handle and a handle stylet thereof        with the hollow insertion needle;    -   connecting the needle-withdrawal handle to the hollow insertion        needle;    -   proximally withdrawing the hollow insertion needle from the        intervertebral disc, while holding the needle-withdrawal handle        stationary, and while the handle stylet abuts the proximal end        of the electrode, thereby preventing proximal motion of the        electrode; and    -   proximally withdrawing the needle-withdrawal handle, thereby        releasing the electrode and leaving the electrode implanted        partially in the intervertebral disc and partially in the body        of the subject outside the intervertebral disc.

For some applications, inserting the hollow insertion needle compriseslimiting a depth of penetration of the hollow insertion needle into theintervertebral disc by inserting the hollow insertion needle into theintervertebral disc until a spacer, through which the hollow insertionneedle passes, contacts an external surface of an annulus fibrosis ofthe intervertebral disc. For some applications, connecting theneedle-withdrawal handle to the hollow insertion needle comprisesconnecting the needle-withdrawal handle to the spacer. For someapplications, proximally withdrawing the needle-withdrawal handlecomprises proximally withdrawing the needle-withdrawal handle while thespacer is attached to the needle-withdrawal handle.

For some applications, the hollow insertion needle is axially fixed to aneedle-connection fitting. Connecting the needle-withdrawal handle tothe hollow insertion needle comprises disposing (a) theneedle-connection fitting within the needle-withdrawal handle, and (b) adistal end of the handle stylet within the needle-connection fittingabutting the proximal end of the electrode. Proximally withdrawing thehollow insertion needle comprises proximally withdrawing theneedle-connection fitting within the needle-withdrawal handle, while theneedle-withdrawal handle is held stationary.

In some applications of the present invention, theintervertebral-disc-treatment system comprises:

-   -   at least one intra-pulposus exposed electrode surface, which is        configured to be implanted in the nucleus pulposus of the        intervertebral disc;    -   a plurality of extra-pulposus exposed electrode surfaces, which        are configured to be implanted outside the nucleus pulposus, in        electrical communication with the intervertebral disc; and    -   the control circuitry, which is (a) electrically coupled to the        at least one intra-pulposus exposed electrode surface and the        plurality of the extra-pulposus exposed electrode surfaces, (b)        configured to separately control at least two of the plurality        of the extra-pulposus exposed electrode surfaces; for example,        the control circuitry may be electrically coupled to the        extra-pulposus exposed electrode surfaces separately via        separate electrical conductors.

Providing the plurality of separately-controllable the extra-pulposusexposed electrode surfaces distributes the generation of hydrogen,thereby reducing any local build-up of hydrogen at any single electrodesurface.

For some applications, the control circuitry is configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and one or more of the plurality of the extra-pulposus        exposed electrode surfaces to be one or more respective anodes,        and (b) electroosmotically drive fluid into the nucleus pulposus        to increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V (sometimes known in the        art as the “electrolysis voltage”) between the at least one        intra-pulposus exposed electrode surface and the one or more of        the plurality of the extra-pulposus exposed electrode surfaces,        and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the plurality of the extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the        plurality of the extra-pulposus exposed electrode surfaces.

The increase in fluid in the nucleus pulposus during thepressure-increasing mode of operation generally treats or preventsfurther degeneration of the disc caused at least in part by loss offluid. The applied current may also help introduce nutritionalsubstances into the disc. The generation of oxygen within the nucleuspulposus during the oxygen-generating mode generally treats hypoxia,which, if untreated, sometimes causes disc degeneration. The generationof oxygen may also improve glucose metabolism, while reducing lacticacid generation.

For some applications, the control circuitry is configured to applydirect current, e.g., with an average amplitude of between 1 and 5 mA.For some applications, the control unit is configured to apply thedirect current as a series of pulses. For some applications, the controlunit is configured to apply the direct current as the series of pulseswith a duty cycle of between 1% and 50%.

Typically, the control circuitry is configured to separately control allof the plurality of the extra-pulposus exposed electrode surfaces; forexample, the control circuitry may be electrically coupled to theextra-pulposus exposed electrode surfaces separately via separateelectrical conductors.

For some applications, the control circuitry is configured, during aperiod of time, to assume (a) the pressure-increasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% of the aggregate first duration.By way of example and not limitation, the control circuitry may assumethe oxygen-generating mode of operation for a few seconds every hour,and assume the pressure-increasing mode of operation at other times.Although the control circuitry, when in the oxygen-generating mode ofoperation, may electroosmotically drive fluid out of the nucleuspulposus and thus decrease pressure in the intervertebral disc, becausethe aggregate second duration is so much less than the aggregate firstduration, the aggregate effect of the application of voltages is anincrease in pressure in the intervertebral disc.

For some applications, the control circuitry is configured to, in theoxygen-generating mode of operation, generate oxygen within the nucleuspulposus by electrolysis, by applying the second mean voltage betweenthe at least one intra-pulposus exposed electrode surface and respectivedifferent subsets of the plurality of the extra-pulposus exposedelectrode surfaces at respective different times. For some applications,each of the subsets consists of exactly one of the plurality of theextra-pulposus exposed electrode surfaces. Activating the extra-pulposusexposed electrode surfaces at different times further distributes thegeneration of hydrogen, thereby further reducing any local build-up ofhydrogen at any single electrode surface.

In some applications of the present invention, theintervertebral-disc-treatment system comprises:

-   -   at least one intra-pulposus exposed electrode surface, which is        configured to be implanted in the nucleus pulposus of the        intervertebral disc;    -   one or more the extra-pulposus exposed electrode surfaces,        which (a) are configured to be implanted outside the nucleus        pulposus, in electrical communication with the intervertebral        disc, and (b) have an aggregate electrically-exposed surface        area of at least 3 cm2, such as at least 4 cm2, e.g., at least 5        cm2; and    -   the control circuitry, which is electrically coupled to the at        least one intra-pulposus exposed electrode surface and one or        more the extra-pulposus exposed electrode surfaces.

For some applications, the control circuitry is configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and the one or more extra-pulposus exposed electrode        surfaces to be one or more respective anodes, and (b)        electroosmotically drive fluid into the nucleus pulposus to        increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V between the at least one        intra-pulposus exposed electrode surface and the one or more        extra-pulposus exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the one or more extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the one        or more extra-pulposus exposed electrode surfaces.

The increase in fluid in the nucleus pulposus during thepressure-increasing mode of operation generally treats or preventsfurther degeneration of the disc caused at least in part by loss offluid. The applied current may also help introduce nutritionalsubstances into the disc. The generation of oxygen within the nucleuspulposus during the oxygen-generating mode generally treats hypoxia,which, if untreated, sometimes causes disc degeneration. The generationof oxygen may also improve glucose metabolism, while reducing lacticacid generation. Providing the relatively large aggregateelectrically-exposed surface area of at least 3 cm2 distributes thegeneration of hydrogen, thereby reducing any local build-up of hydrogenat the electrode-tissue interface.

For some applications, the intervertebral-disc-treatment systemcomprises exactly one extra-pulposus exposed electrode surface having anelectrically-exposed surface area of at least 3 cm2. Alternatively, anexternal surface of a can of the control circuitry serves as theextra-pulposus exposed electrode surface. For other applications, theintervertebral-disc-treatment system comprises a plurality of theextra-pulposus exposed electrode surfaces.

For some applications, the control circuitry is configured to applydirect current, e.g., with an average amplitude of between 1 and 5 mA.For some applications, the control unit is configured to apply thedirect current as a series of pulses. For some applications, the controlunit is configured to apply the direct current as the series of pulseswith a duty cycle of between 1% and 50%.

For some applications, the control circuitry is configured, during aperiod of time, to assume (a) the pressure-increasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% of the aggregate first duration.By way of example and not limitation, the control circuitry may assumethe oxygen-generating mode of operation for a few seconds every hour,and assume the pressure-increasing mode of operation at other times.Although the control circuitry, when in the oxygen-generating mode ofoperation, may electroosmotically drive fluid out of the nucleuspulposus and thus decrease pressure in the intervertebral disc, becausethe aggregate second duration is so much less than the aggregate firstduration, the aggregate effect of the application of voltages is anincrease in pressure in the intervertebral disc.

There is therefore provided, in accordance with an inventive concept 1of the present invention, apparatus for treating an intervertebral discof a subject, the apparatus including:

at least one intra-pulposus exposed electrode surface, which isconfigured to be implanted in a nucleus pulposus of the intervertebraldisc;

a plurality of extra-pulposus exposed electrode surfaces, which areconfigured to be implanted outside the nucleus pulposus, in electricalcommunication with the intervertebral disc; and

control circuitry, which is (a) electrically coupled to the at least oneintra-pulposus exposed electrode surface and the plurality ofextra-pulposus exposed electrode surfaces, (b) configured to separatelycontrol at least two of the plurality of extra-pulposus exposedelectrode surfaces, and (c) configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and one or more of the plurality of extra-pulposus        exposed electrode surfaces to be one or more respective anodes,        and (b) electroosmotically drive fluid into the nucleus pulposus        to increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V between the at least one        intra-pulposus exposed electrode surface and the one or more of        the plurality of extra-pulposus exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the plurality of extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the        plurality of extra-pulposus exposed electrode surfaces.        Inventive concept 2. The apparatus according to inventive        concept 1, wherein the control circuitry is configured to        separately control all of the plurality of extra-pulposus        exposed electrode surfaces.        Inventive concept 3. The apparatus according to inventive        concept 1, wherein the first mean voltage is less than 500 mV.        Inventive concept 4. The apparatus according to inventive        concept 3, wherein the first mean voltage is less than 300 mV.        Inventive concept 5. The apparatus according to inventive        concept 1, wherein the second mean voltage is at least 2 V.        Inventive concept 6. The apparatus according to any one of        inventive concepts 1-5, wherein the control circuitry is        configured, during a period of time, to assume (a) the        pressure-increasing mode of operation at least 10 times for an        aggregate first duration and (b) the oxygen-generating mode of        operation at least 10 times for an aggregate second duration        that is less than 10% of the aggregate first duration.        Inventive concept 7. The apparatus according to inventive        concept 6, wherein the aggregate second duration is less than 5%        of the aggregate first duration.        Inventive concept 8. The apparatus according to inventive        concept 7, wherein the aggregate second duration is less than 1%        of the aggregate first duration.        Inventive concept 9. The apparatus according to any one of        inventive concepts 1-5, wherein the plurality of extra-pulposus        exposed electrode surfaces includes at least three        extra-pulposus exposed electrode surfaces.        Inventive concept 10. The apparatus according to inventive        concept 9, wherein the plurality of extra-pulposus exposed        electrode surfaces includes up to 10 extra-pulposus exposed        electrode surfaces.        Inventive concept 11. The apparatus according to any one of        inventive concepts 1-5, wherein the control circuitry is        configured to, in the oxygen-generating mode of operation,        generate oxygen within the nucleus pulposus by electrolysis, by        applying the second mean voltage between the at least one        intra-pulposus exposed electrode surface and respective        different subsets of the plurality of extra-pulposus exposed        electrode surfaces at respective different times.        Inventive concept 12. The apparatus according to inventive        concept 11, wherein each of the subsets consists of exactly one        of the plurality of extra-pulposus exposed electrode surfaces.        Inventive concept 13. The apparatus according to any one of        inventive concepts 1-5,

wherein the apparatus further includes a sensor, which is configured tosense a parameter indicative of a quantity of the oxygen generated bythe electrolysis, and

wherein the control circuitry is configured to modulate theoxygen-generating mode of operation responsively to the sensedparameter.

Inventive concept 14. The apparatus according to inventive concept 13,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating a duration of one ormore occurrences of the oxygen-generating mode of operation.Inventive concept 15. The apparatus according to inventive concept 13,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating an electricalparameter of the second mean voltage.Inventive concept 16. The apparatus according to inventive concept 13,wherein the sensed parameter is an oxygen concentration in the nucleuspulposus.Inventive concept 17. The apparatus according to inventive concept 13,wherein the sensed parameter is a pH in the nucleus pulposus.

There is further provided, in accordance with an inventive concept 18 ofthe present invention, apparatus for treating an intervertebral disc ofa subject, the apparatus including:

at least one intra-pulposus exposed electrode surface, which isconfigured to be implanted in a nucleus pulposus of the intervertebraldisc;

one or more extra-pulposus exposed electrode surfaces, which (a) areconfigured to be implanted outside the nucleus pulposus, in electricalcommunication with the intervertebral disc, and (b) have an aggregateelectrically-exposed surface area of at least 1 cm2; and

control circuitry, which is (a) electrically coupled to the at least oneintra-pulposus exposed electrode surface and one or more extra-pulposusexposed electrode surfaces, and (b) configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and the one or more extra-pulposus exposed electrode        surfaces to be one or more respective anodes, and (b)        electroosmotically drive fluid into the nucleus pulposus to        increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V between the at least one        intra-pulposus exposed electrode surface and the one or more        extra-pulposus exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the one or more extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the one        or more extra-pulposus exposed electrode surfaces.        Inventive concept 19. The apparatus according to inventive        concept 18, wherein the aggregate electrically-exposed surface        area is at least 3 cm2.        Inventive concept 20. The apparatus according to inventive        concept 18, wherein the first mean voltage is less than 500 mV.        Inventive concept 21. The apparatus according to inventive        concept 20, wherein the first mean voltage is less than 300 mV.        Inventive concept 22. The apparatus according to inventive        concept 18, wherein the second mean voltage is at least 2 V.        Inventive concept 23. The apparatus according to any one of        inventive concepts 18-22, wherein the control circuitry is        configured, during a period of time, to assume (a) the        pressure-increasing mode of operation at least 10 times for an        aggregate first duration and (b) the oxygen-generating mode of        operation at least 10 times for an aggregate second duration        that is less than 10% of the aggregate first duration.        Inventive concept 24. The apparatus according to inventive        concept 23, wherein the aggregate second duration is less than        5% of the aggregate first duration.        Inventive concept 25. The apparatus according to inventive        concept 24, wherein the aggregate second duration is less than        1% of the aggregate first duration.        Inventive concept 26. The apparatus according to any one of        inventive concepts 18-22, wherein the apparatus includes exactly        one extra-pulposus exposed electrode surface having an        electrically-exposed surface area of at least 1 cm2.        Inventive concept 27. The apparatus according to inventive        concept 26, wherein the surface area of the of the exactly one        extra-pulposus exposed electrode surface is at least 3 cm2.        Inventive concept 28. The apparatus according to any one of        inventive concepts 18-22, wherein the apparatus includes a        plurality of extra-pulposus exposed electrode surfaces.        Inventive concept 29. The apparatus according to inventive        concept 18,

wherein the apparatus further includes a sensor, which is configured tosense a parameter indicative of a quantity of the oxygen generated bythe electrolysis, and

wherein the control circuitry is configured to modulate theoxygen-generating mode of operation responsively to the sensedparameter.

Inventive concept 30. The apparatus according to inventive concept 29,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating a duration of one ormore occurrences of the oxygen-generating mode of operation.Inventive concept 31. The apparatus according to inventive concept 29,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating an electricalparameter of the second mean voltage.Inventive concept 32. The apparatus according to inventive concept 29,wherein the sensed parameter is an oxygen concentration in the nucleuspulposus.Inventive concept 33. The apparatus according to inventive concept 29,wherein the sensed parameter is a pH in the nucleus pulposus.

There is still further provided, in accordance with an inventive concept34 of the present invention, a method for treating an intervertebraldisc of a subject, the method including:

implanting at least one intra-pulposus exposed electrode surface in anucleus pulposus of the intervertebral disc;

implanting a plurality of extra-pulposus exposed electrode surfacesoutside the nucleus pulposus, in electrical communication with theintervertebral disc; and

activating control circuitry, which is (a) electrically coupled to theat least one intra-pulposus exposed electrode surface and the pluralityof extra-pulposus exposed electrode surfaces, and (b) configured toseparately control at least two of the plurality of extra-pulposusexposed electrode surfaces, to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and one or more of the plurality of extra-pulposus        exposed electrode surfaces to be one or more respective anodes,        and (b) electroosmotically drive fluid into the nucleus pulposus        to increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V between the at least one        intra-pulposus exposed electrode surface and the one or more of        the plurality of extra-pulposus exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the plurality of extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the        plurality of extra-pulposus exposed electrode surfaces.

There is additionally provided, in accordance with an inventive concept35 of the present invention, a method for treating an intervertebraldisc of a subject, the method including:

implanting at least one intra-pulposus exposed electrode surface in anucleus pulposus of the intervertebral disc;

implanting one or more extra-pulposus exposed electrode surfaces outsidethe nucleus pulposus, in electrical communication with theintervertebral disc, the one or more extra-pulposus exposed electrodesurfaces having an aggregate electrically-exposed surface area of atleast 1 cm2; and

activating control circuitry, which is electrically coupled to the atleast one intra-pulposus exposed electrode surface and one or moreextra-pulposus exposed electrode surfaces, to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface to be a        cathode, and the one or more extra-pulposus exposed electrode        surfaces to be one or more respective anodes, and (b)        electroosmotically drive fluid into the nucleus pulposus to        increase pressure in the intervertebral disc, by applying a        first mean voltage of less than 1.23 V between the at least one        intra-pulposus exposed electrode surface and the one or more        extra-pulposus exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface to be an        anode, and the one or more extra-pulposus exposed electrode        surfaces to be a respective plurality of cathodes, and (b)        generate oxygen within the nucleus pulposus by electrolysis, by        applying a second mean voltage of at least 1.23 V between the at        least one intra-pulposus exposed electrode surface and the one        or more extra-pulposus exposed electrode surfaces.

There is yet additionally provided, in accordance with an inventiveconcept 36 of the present invention, apparatus including an electrode,which includes a wire that (a) has a wire diameter of between 75 and 125microns and (b) includes:

a non-electrically-insulated current-application longitudinal segment,which, in the absence of any applied forces, is coiled and has (i) amean pitch of between 1.1 and 2 times the wire diameter, and (ii) anentire longitudinal length of between 5 and 35 mm, and

an electrically-insulated lead longitudinal segment, which has an entirelongitudinal length of between 5 and 80 mm, in the absence of anyapplied forces.

Inventive concept 37. The apparatus according to inventive concept 36,wherein the mean pitch of the current-application longitudinal segmentis between 1.2 and 1.8 times the wire diameter, in the absence of anyapplied forces.

Inventive concept 38. The apparatus according to inventive concept 37,wherein the mean pitch of the current-application longitudinal segmentis between 1.4 and 1.6 times the wire diameter, in the absence of anyapplied forces.

Inventive concept 39. The apparatus according to inventive concept 36,wherein the wire diameter is between 90 and 110 microns.

Inventive concept 40. The apparatus according to inventive concept 39,wherein the wire diameter of is between 95 and 105 microns.

Inventive concept 41. The apparatus according to inventive concept 36,wherein the current-application longitudinal segment has an outer coildiameter of between 3 and 7 times the wire diameter, in the absence ofany applied forces.

Inventive concept 42. The apparatus according to inventive concept 41,wherein the outer coil diameter of the current-application longitudinalsegment is between 4 and 6 times the wire diameter, in the absence ofany applied forces.

Inventive concept 43. The apparatus according to inventive concept 36,wherein the current-application longitudinal segment has an outer coildiameter of between 400 and 600 microns, in the absence of any appliedforces.

Inventive concept 44. The apparatus according to inventive concept 36,wherein the entire longitudinal length of the current-applicationlongitudinal segment is between 10 and 25 mm, in the absence of anyapplied forces.

Inventive concept 45. The apparatus according to inventive concept 36,wherein the entire longitudinal length of the electrically-insulatedlead longitudinal segment is between 10 and 50 mm, in the absence of anyapplied forces.

Inventive concept 46. The apparatus according to inventive concept 36,wherein, when a central longitudinal axis of a 3-mm long portion of thecurrent-application longitudinal segment is curved in a plane only untilall adjacent turns of the coiled wire of the portion touch one another,the central longitudinal axis of the portion has a radius of curvatureof between 5 and 10 mm.Inventive concept 47. The apparatus according to inventive concept 36,wherein the current-application longitudinal segment extends to a distalend of the wire.Inventive concept 48. The apparatus according to inventive concept 36,wherein the electrically-insulated lead longitudinal segment is coatedwith parylene.Inventive concept 49. The apparatus according to inventive concept 36,wherein the lead longitudinal segment is not coiled, in the absence ofany applied forces.Inventive concept 50. The apparatus according to any one of inventiveconcepts 36-49, wherein the lead longitudinal segment is coiled, in theabsence of any applied forces.Inventive concept 51. The apparatus according to inventive concept 50,wherein the lead longitudinal segment has a mean pitch that is greaterthan the mean pitch of the current-application longitudinal segment, inthe absence of any applied forces.Inventive concept 52. The apparatus according to inventive concept 51,wherein the mean pitch of the lead longitudinal segment is at least 125%of the mean pitch of the current-application longitudinal segment, inthe absence of any applied forces.Inventive concept 53. The apparatus according to inventive concept 52,wherein the mean pitch of the lead longitudinal segment is at least 150%of the mean pitch of the current-application longitudinal segment, inthe absence of any applied forces.Inventive concept 54. The apparatus according to inventive concept 50,wherein the lead longitudinal segment has a mean pitch of between 2 and3 times the wire diameter, in the absence of any applied forces.Inventive concept 55. The apparatus according to inventive concept 54,wherein the mean pitch of the lead longitudinal segment is between 2.2and 2.8 times the wire diameter, in the absence of any applied forces.Inventive concept 56. The apparatus according to inventive concept 55,wherein the mean pitch of the lead longitudinal segment is between 2.4and 2.6 times the wire diameter, in the absence of any applied forces.Inventive concept 57. The apparatus according to inventive concept 50,wherein the lead longitudinal segment has an outer coil diameter thatequals between 90% and 110% of an outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 58. The apparatus according to inventive concept 57,wherein the outer coil diameter of the lead longitudinal segment equalsthe outer coil diameter of the current-application longitudinal segment,in the absence of any applied forces.Inventive concept 59. The apparatus according to inventive concept 50,wherein the lead longitudinal segment has an outer coil diameter ofbetween 3 and 7 times the wire diameter, in the absence of any appliedforces.Inventive concept 60. The apparatus according to inventive concept 59,wherein the outer coil diameter of the lead longitudinal segment isbetween 4 and 6 times the wire diameter, in the absence of any appliedforces.Inventive concept 61. The apparatus according to any one of inventiveconcepts 36-49, wherein the wire further includes an intermediatelongitudinal segment, which (a) is longitudinally between thecurrent-application longitudinal segment and the lead longitudinalsegment, (b) has an entire longitudinal length of between 1 and 6 mm, inthe absence of any applied forces, and (c) in the absence of any appliedforces, either (i) is coiled, and has a mean pitch greater than an outercoil diameter of the current-application longitudinal segment or (ii) isnot coiled.Inventive concept 62. The apparatus according to inventive concept 61,wherein the intermediate longitudinal segment is electrically insulatedalong at least a longitudinal portion of the intermediate longitudinalsegment.Inventive concept 63. The apparatus according to inventive concept 61,wherein the intermediate longitudinal segment is not coiled, in theabsence of any applied forces.Inventive concept 64. The apparatus according to inventive concept 61,wherein the entire longitudinal length of the intermediate longitudinalsegment is between 2 and 4 mm, in the absence of any applied forces.Inventive concept 65. The apparatus according to inventive concept 61,wherein, in the absence of any applied forces, the intermediatelongitudinal segment is coiled, and has the mean pitch greater than theouter coil diameter of the current-application longitudinal segment.Inventive concept 66. The apparatus according to inventive concept 65,wherein the mean pitch of the intermediate longitudinal segment isbetween 125% and 250% of the outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 67. The apparatus according to inventive concept 65,wherein an outer coil diameter of the intermediate longitudinal segmentequals between 90% and 110% of the outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 68. The apparatus according to inventive concept 67,wherein the outer coil diameter of the intermediate longitudinal segmentequals the outer coil diameter of the current-application longitudinalsegment, in the absence of any applied forces.Inventive concept 69. The apparatus according to inventive concept 65,wherein the intermediate longitudinal segment has a mean pitch ofbetween 5 and 20 times the wire diameter, in the absence of any appliedforces.Inventive concept 70. The apparatus according to inventive concept 69,wherein the mean pitch of the intermediate longitudinal segment isbetween 6 and 13 times the wire diameter, in the absence of any appliedforces.Inventive concept 71. The apparatus according to inventive concept 70,wherein the mean pitch of the intermediate longitudinal segment isbetween 9 and 11 times the wire diameter, in the absence of any appliedforces.Inventive concept 72. The apparatus according to inventive concept 65,wherein the intermediate longitudinal segment has an outer coil diameterof between 3 and 7 times the wire diameter, in the absence of anyapplied forces.Inventive concept 73. The apparatus according to inventive concept 72,wherein the outer coil diameter of the intermediate longitudinal segmentis between 4 and 6 times the wire diameter, in the absence of anyapplied forces.Inventive concept 74. The apparatus according to any one of inventiveconcepts 36-49,

wherein the wire further includes a partially non-electrically-insulatedpin-connector longitudinal segment,

wherein the lead longitudinal segment is longitudinally between thecurrent-application longitudinal segment and the pin-connectorlongitudinal segment, and

wherein the apparatus includes an electrode assembly, which includes theelectrode and a pin, which is mechanically fixed to and in electricalcommunication with the pin-connector longitudinal segment.

Inventive concept 75. The apparatus according to inventive concept 74,wherein the pin is shaped so as to define a lumen.

Inventive concept 76. The apparatus according to inventive concept 75,wherein the pin-connector longitudinal segment is at least partiallydisposed in the lumen of the pin.

Inventive concept 77. The apparatus according to inventive concept 76,wherein the pin is crimped on the pin-connector longitudinal segment.

Inventive concept 78. The apparatus according to inventive concept 74,wherein the pin-connector longitudinal segment is not coiled, in theabsence of any applied forces.

Inventive concept 79. The apparatus according to inventive concept 78,wherein the pin-connector longitudinal segment is coaxial with a centrallongitudinal axis of the electrically-insulated lead longitudinalsegment, in the absence of any applied forces.

Inventive concept 80. The apparatus according to inventive concept 74,wherein the pin-connector longitudinal segment is coiled, in the absenceof any applied forces.

Inventive concept 81. The apparatus according to inventive concept 80,wherein the pin-connector longitudinal segment has a mean pitch thatequals at least 125% of an outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 82. The apparatus according to inventive concept 81,wherein the mean pitch of the pin-connector longitudinal segment is atbetween 125% and 250% of the outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 83. The apparatus according to inventive concept 80,wherein the pin-connector longitudinal segment has an outer coildiameter that equals between 90% and 110% of an outer coil diameter ofthe current-application longitudinal segment, in the absence of anyapplied forces.Inventive concept 84. The apparatus according to inventive concept 83,wherein the outer coil diameter of the pin-connector longitudinalsegment equals the outer coil diameter of the current-applicationlongitudinal segment, in the absence of any applied forces.Inventive concept 85. The apparatus according to inventive concept 80,wherein the pin-connector longitudinal segment, in the absence of anyapplied forces, has (a) a mean pitch of between 5 and 20 times the wirediameter, and (b) an entire longitudinal length of between 1 and 4 mm.Inventive concept 86. The apparatus according to inventive concept 85,wherein the mean pitch of the pin-connector longitudinal segment isbetween 5 and 10 times the wire diameter, in the absence of any appliedforces.Inventive concept 87. The apparatus according to inventive concept 80,wherein the pin-connector longitudinal segment has an outer coildiameter of between 3 and 7 times the wire diameter, in the absence ofany applied forces.Inventive concept 88. The apparatus according to inventive concept 87,wherein the outer coil diameter of the pin-connector longitudinalsegment is between 4 and 6 times the wire diameter, in the absence ofany applied forces.Inventive concept 89. The apparatus according to any one of inventiveconcepts 36-49,

wherein the wire further includes an intermediate longitudinal segment,which (a) is longitudinally between the current-application longitudinalsegment and the lead longitudinal segment, and (b) has an entirelongitudinal length of between 1 and 6 mm, in the absence of any appliedforces, and

wherein the electrode further includes a water-permeable element thatsurrounds at least a longitudinal portion of the intermediatelongitudinal segment.

Inventive concept 90. The apparatus according to inventive concept 89,wherein the water-permeable element includes a membrane.

Inventive concept 91. The apparatus according to inventive concept 89,wherein the water-permeable element includes an acid selected from thegroup consisting of: glycolic acid and lactic acid.

Inventive concept 92. The apparatus according to inventive concept 89,wherein the intermediate longitudinal segment is coiled, in the absenceof any applied forces.

Inventive concept 93. The apparatus according to inventive concept 92,wherein the intermediate longitudinal segment, in the absence of anyapplied forces, has a mean pitch that equals (a) at least the mean pitchof the current-application longitudinal segment, and (b) no more thanthe mean pitch of the lead longitudinal segment.Inventive concept 94. The apparatus according to any one of inventiveconcepts 36-49, further including control circuitry, which iselectrically coupled to the electrode, and which is configured to drivethe electrode to apply a current.

There is also provided, in accordance with an inventive concept 95 ofthe present invention, apparatus including an electrode, which includesa wire that (a) has a wire diameter of between 75 and 125 microns and(b) includes a non-electrically-insulated current-applicationlongitudinal segment, which, in the absence of any applied forces, iscoiled and has (i) a mean pitch of between 1.1 and 2 times the wirediameter, and (ii) an entire longitudinal length of between 5 and 35 mm.

There is further provided, in accordance with an inventive concept 96 ofthe present invention, apparatus including an electrode, which includesa wire that includes:

a non-electrically-insulated current-application longitudinal segment,which, in the absence of any applied forces, is coiled and has an entirelongitudinal length of between 5 and 35 mm,

an electrically-insulated lead longitudinal segment, which has an entirelongitudinal length of between 5 and 80 mm, in the absence of anyapplied forces, and

an intermediate longitudinal segment, which (a) is longitudinallybetween the current-application longitudinal segment and the leadlongitudinal segment, (b) has an entire longitudinal length of between 1and 6 mm, in the absence of any applied forces, and (c) in the absenceof any applied forces, either (i) is coiled, and has a mean pitchgreater than an outer coil diameter of the current-applicationlongitudinal segment or (ii) is not coiled.

Inventive concept 97. The apparatus according to inventive concept 96,wherein the intermediate longitudinal segment is electrically insulatedalong at least a longitudinal portion of the intermediate longitudinalsegment.

Inventive concept 98. The apparatus according to inventive concept 96,wherein the intermediate longitudinal segment is not coiled, in theabsence of any applied forces.

Inventive concept 99. The apparatus according to inventive concept 96,wherein the wire has a wire diameter of between 75 and 125 microns.

Inventive concept 100. The apparatus according to any one of inventiveconcepts 96-99, wherein, in the absence of any applied forces, theintermediate longitudinal segment is coiled, and has the mean pitchgreater than the outer coil diameter of the current-applicationlongitudinal segment.Inventive concept 101. The apparatus according to inventive concept 100,wherein the mean pitch of the intermediate longitudinal segment isbetween 125% and 250% of the outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 102. The apparatus according to inventive concept 100,wherein an outer coil diameter of the intermediate longitudinal segmentequals between 90% and 110% of the outer coil diameter of thecurrent-application longitudinal segment, in the absence of any appliedforces.Inventive concept 103. The apparatus according to inventive concept 100,wherein in the absence of any applied forces:

the current-application longitudinal segment has a mean pitch of between1.1 and 2 times a wire diameter of the wire, and

the intermediate longitudinal segment has a mean pitch of between 5 and20 times the wire diameter.

Inventive concept 104. The apparatus according to inventive concept 100,wherein the intermediate longitudinal segment has an outer coil diameterof between 3 and 7 times the wire diameter, in the absence of anyapplied forces.

There is still further provided, in accordance with an inventive concept105 of the present invention, a method including:

providing an electrode, which includes a wire that (a) has a wirediameter of between 75 and 125 microns and (b) includes (i) anon-electrically-insulated current-application longitudinal segment,which, in the absence of any applied forces, is coiled and has (A) amean pitch of between 1.1 and 2 times the wire diameter, and (B) anentire longitudinal length of between 5 and 35 mm, and (ii) anelectrically-insulated lead longitudinal segment has an entirelongitudinal length of between 5 and 80 mm, in the absence of anyapplied forces; and

implanting at least a portion of the electrode in a body of a subject.

Inventive concept 106. The method according to inventive concept 105,wherein implanting the at least a portion of the electrode includesimplanting the at least a portion of the electrode such that:

the current-application longitudinal segment is disposed at leastpartially in an intervertebral disc of the subject, and

at least a portion of the lead longitudinal segment is disposed in thebody of the subject outside the intervertebral disc.

Inventive concept 107. The method according to inventive concept 106,wherein implanting the at least a portion of the electrode includesimplanting the at least a portion of the electrode such that thecurrent-application longitudinal segment is disposed entirely in theintervertebral disc.Inventive concept 108. The method according to inventive concept 107,wherein implanting the at least a portion of the electrode includesimplanting the at least a portion of the electrode such that thecurrent-application longitudinal segment is disposed entirely in anucleus pulposus of the intervertebral disc.Inventive concept 109. The method according to inventive concept 107,wherein implanting the at least a portion of the electrode includesimplanting the at least a portion of the electrode such that thecurrent-application longitudinal segment is disposed partially in anucleus pulposus of the intervertebral disc and partially in an annulusfibrosus of the intervertebral disc.Inventive concept 110. The method according to inventive concept 107,

wherein the wire further includes an intermediate longitudinal segment,which (a) is longitudinally between the current-application longitudinalsegment and the lead longitudinal segment, (b) has an entirelongitudinal length of between 1 and 6 mm, in the absence of any appliedforces, and (c) in the absence of any applied forces, either (i) iscoiled, and has a mean pitch greater than an outer coil diameter of thecurrent-application longitudinal segment or (ii) is not coiled, and

wherein implanting the at least a portion of the electrode includesimplanting the at least a portion of the electrode such that theintermediate longitudinal segment is disposed at least in part in anannulus fibrosus of the intervertebral disc.

There is additionally provided, in accordance with an inventive concept111 of the present invention, a method including:

providing an electrode, which includes a wire that (a) has a wirediameter of between 75 and 125 microns and (b) includes anon-electrically-insulated current-application longitudinal segment,which, in the absence of any applied forces, is coiled and has (a) amean pitch of between 1.1 and 2 times the wire diameter, and (b) anentire longitudinal length of between 5 and 35 mm; and

implanting at least a portion of the electrode in a body of a subject.

There is yet additionally provided, in accordance with an inventiveconcept 112 of the present invention, a method including:

providing an electrode, which includes a wire that includes (a) anon-electrically-insulated current-application longitudinal segment,which, in the absence of any applied forces, is coiled and has an entirelongitudinal length of between 5 and 35 mm, (b) anelectrically-insulated lead longitudinal segment, which has an entirelongitudinal length of between 5 and 80 mm, in the absence of anyapplied forces, and (c) an intermediate longitudinal segment, which (i)is longitudinally between the current-application longitudinal segmentand the lead longitudinal segment, (ii) has an entire longitudinallength of between 1 and 6 mm, in the absence of any applied forces, and(iii) in the absence of any applied forces, either (A) is coiled, andhas a mean pitch greater than an outer coil diameter of thecurrent-application longitudinal segment or (B) is not coiled; andimplanting at least a portion of the electrode in a body of a subject.

There is also provided, in accordance with an inventive concept 113 ofthe present invention, a method of manufacturing an electrode, themethod including:

providing an electrode, which includes a non-electrically-insulated wirethat (A) has a wire diameter of between 75 and 125 microns and (B)includes:

-   -   (a) a current-application longitudinal segment, which, in the        absence of any applied forces, is coiled and has a mean pitch of        between 1.1 and 2 times the wire diameter,    -   (b) a lead longitudinal segment, and    -   (c) an intermediate longitudinal segment, which (i) is        longitudinally between the current-application longitudinal        segment and the lead longitudinal segment, and (ii) in the        absence of any applied forces, either (A) is coiled and has a        mean pitch greater than an outer coil diameter of the        current-application longitudinal segment or (B) is not coiled;

providing a polymer boot that is shaped so as to define an enclosedspace with an opening having a perimeter;

masking a portion of the electrode by placing the boot on the portion ofthe electrode, such that (a) the current-application longitudinalsegment is within the enclosed space, (b) the lead longitudinal segmentis outside the boot, and (c) the intermediate longitudinal segmentpasses through the opening such that the perimeter of the opening formsa tight seal with at least a portion of the intermediate longitudinalsegment;

placing the boot and the electrode into a vapor deposition chamber; and

applying a parylene coating to the lead longitudinal segment by vapordeposition within the vapor deposition chamber.

Inventive concept 114. The method according to inventive concept 113,wherein providing the electrode includes providing the electrode inwhich the current-application longitudinal segment has an entirelongitudinal length of between 5 and 35 mm, in the absence of anyapplied forces.Inventive concept 115. The method according to inventive concept 113,wherein providing the electrode includes providing the electrode inwhich the lead longitudinal segment has an entire longitudinal length ofbetween 5 and 80 mm, in the absence of any applied forces.Inventive concept 116. The method according to inventive concept 113,wherein providing the electrode includes providing the electrode inwhich the intermediate longitudinal segment has an entire longitudinallength of between 1 and 6 mm, in the absence of any applied forces.Inventive concept 117. The method according to inventive concept 113,wherein providing the electrode includes providing the electrode inwhich, in the absence of any applied forces:

the current-application longitudinal segment has an entire longitudinallength of between 5 and 35 mm,

the lead longitudinal segment has an entire longitudinal length ofbetween 5 and 80 mm, and

the intermediate longitudinal segment has an entire longitudinal lengthof between 1 and 6 mm.

Inventive concept 118. The method according to inventive concept 113,wherein providing the polymer boot includes providing a silicone boot.

There is further provided, in accordance with an inventive concept 119of the present invention, apparatus including an electrode and animplantation system for implanting at least a portion of the electrodein a body of a subject, the implantation system including:

a hollow insertion needle configured to be inserted into anintervertebral disc of the subject;

an electrode loader, which (a) includes (i) a hollow loader needle inwhich the electrode is configured to be loaded, and (ii) a loaderstylet, which is configured to be loaded partially in the hollow loaderneedle and to be disposed such that a distal end of the loader styletabuts a proximal end of the electrode, and (b) is configured to beconnected to the hollow insertion needle, such that (i) a distal end ofthe hollow loader needle abuts a proximal end of the hollow insertionneedle, and (ii) the loader stylet pushes the electrode distally fromthe hollow loader needle into the insertion needle when the loaderstylet is distally advanced within the hollow loader needle; and

a needle-withdrawal handle, which (a) includes a handle stylet, and (b)is configured (i) to be connected to the hollow insertion needle, (ii)while held stationary, to proximally withdraw the hollow insertionneedle from the intervertebral disc while the handle stylet abuts theproximal end of the electrode, thereby preventing proximal motion of theelectrode, and (iii) by being proximally withdrawn, to release theelectrode and leave the electrode implanted partially in theintervertebral disc and partially in the body of the subject outside theintervertebral disc.

Inventive concept 120. The apparatus according to inventive concept 119,wherein the implantation system further includes a spacer, which isconfigured to contact an external surface of an annulus fibrosis of theintervertebral disc so as to limit a depth of penetration of the hollowinsertion needle into the intervertebral disc, and wherein the hollowinsertion needle passes through the spacer.Inventive concept 121. The apparatus according to inventive concept 120,wherein the needle-withdrawal handle is configured to be connected tothe hollow insertion needle by connecting the needle-withdrawal handleto the spacer.Inventive concept 122. The apparatus according to inventive concept 121,wherein the needle-withdrawal handle is configured to be proximallywithdrawn by proximally withdrawing the needle-withdrawal handle whilethe spacer is attached to the needle-withdrawal handle.Inventive concept 123. The apparatus according to inventive concept 119,

wherein the implantation system further includes a needle-connectionfitting, which is axially fixed to the hollow insertion needle,

wherein the needle-withdrawal handle is configured such that when theneedle-withdrawal handle is connected to the hollow insertion needle,the needle-connection fitting is disposed within the needle-withdrawalhandle, and a distal end of the handle stylet is disposed within theneedle-connection fitting abutting the proximal end of the electrode,and

wherein the needle-connection fitting is configured to be proximallywithdrawn within the needle-withdrawal handle, while theneedle-withdrawal handle is held stationary, so as to proximallywithdraw the hollow insertion needle.

There is still further provided, in accordance with an inventive concept124 of the present invention, a method of implanting at least a portionof an electrode in a body of a subject, the method including:

inserting a hollow insertion needle into an intervertebral disc of thesubject;

aligning an electrode loader with the hollow insertion needle, while (a)the electrode is preloaded in a hollow loader needle of the electrodeloader, and (b) a loader stylet of the electrode loader is preloadedpartially in the hollow loader needle and disposed such that a distalend of the loader stylet abuts a proximal end of the electrode;

connecting the electrode loader to the hollow insertion needle, suchthat a distal end of the hollow loader needle abuts a proximal end ofthe hollow insertion needle;

advancing the electrode into the hollow insertion needle by advancingthe loader stylet distally within the hollow loader needle so that theloader stylet pushes the electrode distally from the hollow loaderneedle into the insertion needle;

aligning a needle-withdrawal handle and a handle stylet of theneedle-withdrawal handle with the hollow insertion needle;

connecting the needle-withdrawal handle to the hollow insertion needle;

proximally withdrawing the hollow insertion needle from theintervertebral disc, while holding the needle-withdrawal handlestationary, and while the handle stylet abuts the proximal end of theelectrode so as to prevent proximal motion of the electrode; and

proximally withdrawing the needle-withdrawal handle, thereby releasingthe electrode and leaving the electrode implanted partially in theintervertebral disc and partially in the body of the subject outside theintervertebral disc.

Inventive concept 125. The method according to inventive concept 124,wherein inserting the hollow insertion needle includes limiting a depthof penetration of the hollow insertion needle into the intervertebraldisc by inserting the hollow insertion needle into the intervertebraldisc until a spacer, through which the hollow insertion needle passes,contacts an external surface of an annulus fibrosis of theintervertebral disc.Inventive concept 126. The method according to inventive concept 125,wherein connecting the needle-withdrawal handle to the hollow insertionneedle includes connecting the needle-withdrawal handle to the spacer.Inventive concept 127. The method according to inventive concept 126,wherein proximally withdrawing the needle-withdrawal handle includesproximally withdrawing the needle-withdrawal handle while the spacer isattached to the needle-withdrawal handle.Inventive concept 128. The method according to inventive concept 124,

wherein the hollow insertion needle is axially fixed to aneedle-connection fitting,

wherein connecting the needle-withdrawal handle to the hollow insertionneedle includes disposing (a) the needle-connection fitting within theneedle-withdrawal handle, and (b) a distal end of the handle styletwithin the needle-connection fitting abutting the proximal end of theelectrode, and

wherein proximally withdrawing the hollow insertion needle includesproximally withdrawing the needle-connection fitting within theneedle-withdrawal handle, while the needle-withdrawal handle is heldstationary.

There is additionally provided, in accordance with an inventive concept129 of the present invention, apparatus for treating an eye of asubject, the apparatus including:

a first exposed electrode surface, which is configured to be implantedin a vitreous cavity of the eye;

a second exposed electrode surface, which is configured to be implantedin a body of the subject at a site outside the vitreous cavity; and

control circuitry, which is configured to:

-   -   repeatedly assume a pressure-decreasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in both the pressure-decreasing mode of operation and the        oxygen-generating mode of operation, configure the first exposed        electrode surface to be an anode, and the second exposed        electrode surface to be a cathode,    -   in the pressure-decreasing mode of operation, electroosmotically        drive fluid from the vitreous cavity to outside the vitreous        cavity to decrease pressure in the vitreous cavity, by applying        a first mean voltage of less than 1.23 V between the first and        the second exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, generate oxygen        within the vitreous cavity by electrolysis, by applying a second        mean voltage of at least 1.23 V between the first and the second        exposed electrode surfaces.        Inventive concept 130. The apparatus according to inventive        concept 129,

wherein the site is within a Schlemm's canal of the subject, and thesecond exposed electrode surface is configured to be implanted withinthe Schlemm's canal, and

wherein the control circuitry is configured to, in thepressure-decreasing mode of operation, electroosmotically drive thefluid from the vitreous cavity to the Schlemm's canal to decrease thepressure in the vitreous cavity, by applying the first mean voltagebetween the first and the second exposed electrode surfaces.

Inventive concept 131. The apparatus according to inventive concept 129,wherein the first mean voltage is less than 500 mV.

Inventive concept 132. The apparatus according to inventive concept 131,wherein the first mean voltage is less than 300 mV.

Inventive concept 133. The apparatus according to inventive concept 129,wherein the second mean voltage is at least 2 V.

Inventive concept 134. The apparatus according to any one of inventiveconcepts 129-133, wherein the control circuitry is configured, during aperiod of time, to assume (a) the pressure-decreasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% of the aggregate first duration.Inventive concept 135. The apparatus according to inventive concept 134,wherein the aggregate second duration is less than 5% of the aggregatefirst duration.Inventive concept 136. The apparatus according to inventive concept 135,wherein the aggregate second duration is less than 1% of the aggregatefirst duration.Inventive concept 137. The apparatus according to any one of inventiveconcepts 129-133,

wherein the apparatus further includes a sensor, which is configured tosense a parameter indicative of a quantity of the oxygen generated bythe electrolysis, and

wherein the control circuitry is configured to modulate theoxygen-generating mode of operation responsively to the sensedparameter.

Inventive concept 138. The apparatus according to inventive concept 137,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating a duration of one ormore occurrences of the oxygen-generating mode of operation.Inventive concept 139. The apparatus according to inventive concept 137,wherein the control circuitry is configured to modulate theoxygen-generating mode of operation by modulating an electricalparameter of the second mean voltage.Inventive concept 140. The apparatus according to inventive concept 137,wherein the sensed parameter is an oxygen concentration in the vitreouscavity.Inventive concept 141. The apparatus according to inventive concept 137,wherein the sensed parameter is a pH in the vitreous cavity.Inventive concept 142. The apparatus according to any one of inventiveconcepts 129-133, wherein the control circuitry is configured to:

detect a pressure difference between the vitreous cavity and outside thevitreous cavity, and

modulate the pressure-decreasing mode of operation responsively to thepressure difference parameter in response to the detected pressuredifference.

There is yet additionally provided, in accordance with an inventiveconcept 143 of the present invention, a method for treating an eye of asubject, the method including:

implanting a first exposed electrode surface in a vitreous cavity of theeye;

implanting a second exposed electrode surface in a body of the subjectat a site outside the vitreous cavity; and

activating control circuitry to:

-   -   repeatedly assume a pressure-decreasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in both the pressure-decreasing mode of operation and the        oxygen-generating mode of operation, configure the first exposed        electrode surface to be an anode, and the second exposed        electrode surface to be a cathode,    -   in the pressure-decreasing mode of operation, electroosmotically        drive fluid from the vitreous cavity to outside the vitreous        cavity to decrease pressure in the vitreous cavity, by applying        a first mean voltage of less than 1.23 V between the first and        the second exposed electrode surfaces, and    -   in the oxygen-generating mode of operation, generate oxygen        within the vitreous cavity by electrolysis, by applying a second        mean voltage of at least 1.23 V between the first and the second        exposed electrode surfaces.        Inventive concept 144. The method according to inventive concept        143,

wherein the site is within a Schlemm's canal of the subject, and whereinimplanting the second exposed electrode surface includes implanting thesecond exposed electrode surface within the Schlemm's canal, and

wherein activating the control circuitry includes activating the controlcircuitry to, in the pressure-decreasing mode of operation,electroosmotically drive the fluid from the vitreous cavity to theSchlemm's canal to decrease the pressure in the vitreous cavity, byapplying the first mean voltage between the first and the second exposedelectrode surfaces.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an intervertebral-disc-treatmentsystem for treating an intervertebral disc of a subject, in accordancewith an application of the present invention;

FIG. 2 is a schematic illustration of an electrode of theintervertebral-disc-treatment system of FIG. 1, in accordance with anapplication of the present invention;

FIG. 3A is a schematic illustration of another configuration of theelectrode of FIG. 2, in accordance with an application of the presentinvention;

FIG. 3B is a schematic illustration of yet another configuration of theelectrode of FIG. 2, in accordance with an application of the presentinvention;

FIG. 4 is a schematic illustration of a 3-mm long portion of acurrent-application longitudinal segment of the electrode of FIG. 2,FIG. 3A, or FIG. 3B, in accordance with an application of the presentinvention;

FIG. 5 is a schematic illustration of another configuration of theelectrode of FIG. 2, in accordance with an application of the presentinvention;

FIG. 6 is a flow chart illustrating a method of manufacturing theelectrode of FIG. 2, of FIG. 3A, or of FIG. 3B, in accordance with anapplication of the present invention;

FIG. 7 is a schematic illustration of a polymer boot used in themanufacturing method of FIG. 6, in accordance with an application of thepresent invention;

FIG. 8 is schematic illustrations of an implantation system forimplanting at least a portion of the electrode of FIG. 2 in a body of asubject, in accordance with an application of the present invention;

FIGS. 9A-B are schematic illustrations of several components of theimplantation system of FIG. 8, in accordance with an application of thepresent invention;

FIG. 10 is a flow chart illustrating a method of implanting at least aportion of the electrode of FIG. 2 in a body of a subject, in accordancewith an application of the present invention;

FIGS. 11A-B are schematic illustrations of a needle insertion step ofthe implantation method of FIG. 10, in accordance with an application ofthe present invention;

FIG. 12 is a schematic illustration of an anti-coring stylet retractionstep of the implantation method of FIG. 10, in accordance with anapplication of the present invention;

FIGS. 13A-C are schematic illustrations of an electrode loader alignmentstep of the implantation method of FIG. 10, in accordance with anapplication of the present invention;

FIGS. 14A-B are schematic illustrations of an electrode-loaderconnection step of the implantation method of FIG. 10, in accordancewith an application of the present invention;

FIGS. 15A-B are schematic illustrations of an electrode advancement stepof the implantation method of FIG. 10, in accordance with an applicationof the present invention;

FIGS. 16A-C are schematic illustrations of a needle-withdrawal-handlealignment step of the implantation method of FIG. 10, in accordance withan application of the present invention;

FIGS. 17A-B are schematic illustrations of a needle-withdrawal-handleconnection step of the implantation method of FIG. 10, in accordancewith an application of the present invention;

FIGS. 18A-C are schematic illustrations of an insertion-needlewithdrawal step of the implantation method of FIG. 10, in accordancewith an application of the present invention;

FIG. 19 is a schematic illustration of a needle-withdrawal-handlewithdrawal step of the implantation method of FIG. 10, in accordancewith an application of the present invention;

FIG. 20 is a schematic illustration of the electrode of FIG. 2 implantedpartially in the disc and partially in the body of the subject outsidethe disc, in accordance with an application of the present invention;

FIG. 21 is a schematic illustration of another configuration of theintervertebral-disc-treatment system of FIG. 1, in accordance with anapplication of the present invention;

FIG. 22 is a schematic illustration of an eye-treatment system fortreating an eye of a subject, in accordance with an application of thepresent invention; and

FIG. 23 is a schematic illustration of a diabetic-retinopathy-treatmentsystem for treating diabetic retinopathy, in accordance with anapplication of the present invention.

DETAILED DESCRIPTION OF APPLICATIONS

FIG. 1 is a schematic illustration of an intervertebral-disc-treatmentsystem 20 for treating an intervertebral disc 30 of a subject, inaccordance with an application of the present invention.Intervertebral-disc-treatment system 20 comprises (a) an electrode 22,which is configured to be implanted (typically chronically) partiallywithin a nucleus pulposus 42 of disc 30, and (b) one or moreextra-pulposus exposed electrode surfaces 44, which are configured to beimplanted (typically chronically) outside nucleus pulposus 42, inelectrical communication with disc 30, in a vicinity of an externalsurface of an annulus fibrosus 46 of disc 30, e.g., in physical contactwith the external surface or not in physical contact with the externalsurface. Intervertebral-disc-treatment system 20 further comprisesimplantable (typically chronically implantable) or external controlcircuitry 50, which is typically electrically coupled, by one or moreelectrode leads 52, to (a) exposed electrode surfaces 44 and (b)electrode 22, such as via pin 76, described hereinbelow with referenceto FIG. 2.

Typically, a healthcare worker, such as a physician, activates controlcircuitry 50 to provide the functions described herein. Activating thecontrol circuitry may include configuring parameters and/or functions ofthe control circuitry (such as using a separate programmer or externalcontroller), or activating the control circuitry to perform functionspre-programmed in the control circuitry. Control circuitry 50 typicallycomprises appropriate memory, processor(s), and hardware runningsoftware that is configured to provide the functionality of the controlcircuitry described herein.

Reference is made to FIG. 2, which is a schematic illustration ofelectrode 22, in accordance with an application of the presentinvention. Electrode 22 comprises a wire 60, which typically has a wirediameter D_(W) of at least 50 microns (more typically at least 75microns, such as at least 90 microns, e.g., at least 95 microns), nomore than 150 microns (more typically no more than 125 microns, such asno more than 110 microns, e.g., no more than 105 microns), and/orbetween 50 microns (more typically 75 microns, such as 90 microns, e.g.,95 microns) and 150 microns (more typically 125 microns, such as 110microns, e.g., 105 microns), such as 100 microns.

Wire 60 includes:

-   -   a non-electrically-insulated current-application longitudinal        segment 62, which, in the absence of any applied forces, is        helically coiled (referred to simply as “coiled” herein,        including in the claims) and typically has (a) a mean pitch P₁        of at least 1.1 (e.g., at least 1.2, such as at least 1.4), no        more than 2 (e.g., no more than 1.8, such as no more than 1.6),        and/or between 1.1 and 2 (e.g., between 1.2 and 1.8, such as        between 1.4 and 1.6, e.g., 1.5) times the wire diameter D_(W),        and (b) an entire longitudinal length L₁ of at least 5 mm (e.g.,        at least 10 mm), no more than 35 mm (e.g., no more than 25 mm),        and/or between 5 and 35 mm (e.g., between 10 and 25 mm), and    -   an electrically-insulated lead longitudinal segment 64, which        typically has an entire longitudinal length L₂ of at least 5 mm        (e.g., at least 10 mm), no more than 80 mm (e.g., no more than        50 mm), and/or between 5 and 80 mm (e.g., between 10 and 50 mm),        in the absence of any applied forces.

As used in the present application, including in the claims, the pitchof a coil is the distance from any point on the coil to thecorresponding point on an adjacent coil measured parallel to the centrallongitudinal axis. As used in the present application, including in theclaims, the longitudinal length of segment is measured in a line along acentral longitudinal axis of the segment (rather than being measuredaround the coil itself of the wire).

Typically, current-application longitudinal segment 62 extends to adistal end 66 of wire 60. For some applications, electrode 22 has atotal length of at 50 mm (e.g., at least 70 mm), no more than 110 mm(e.g., no more than 90 mm), and/or between 50 and 110 mm (e.g., between70 and 90 mm), such as 80 mm.

For some applications, electrically-insulated lead longitudinal segment64 is coated with parylene, or another biocompatible non-conductingmaterial known in the art.

For some applications, current-application longitudinal segment 62 hasan outer coil diameter C₁ of at least 3 (e.g., at least 4), no more than7 (e.g., no more than 6), and/or between 3 and 7 (e.g., between 4 and6), e.g., 5, times the wire diameter D_(W), in the absence of anyapplied forces. Alternatively or additionally, for some applications,the outer coil diameter C₁ is at least 400 microns (e.g., at least 450microns), no more than 600 microns (e.g., no more than 550 microns),and/or between 400 and 600 microns (e.g., between 450 and 550 microns),e.g., 500 microns, in the absence of any applied forces.

Typically, because of the above-mentioned dimensions, including thepitch, current-application longitudinal segment 62 is highly flexible(both in its ability to bend and its ability to longitudinally stretchand contract), which reduces the application of forces on intervertebraldisc 30, and thus generally causes no or less trauma to intervertebraldisc 30, including nucleus pulposus 42, than a more rigid electrodemight cause, particularly over time during repeated motion of the disc.

For some applications, lead longitudinal segment 64 is coiled, in theabsence of any applied forces, such as shown in the figures. For someapplications, lead longitudinal segment 64 has one or more of thefollowing dimensions, in the absence of any applied forces:

-   -   a mean pitch P₂ that is greater than (such as at least 125% of,        e.g., at least 150% of, at least 175% of, at least 200% of, or        at least 250% of) the mean pitch P₁ of current-application        longitudinal segment 62,    -   a mean pitch P₂ of at least 2 (e.g., at least 2.2, such as at        least 2.4), no more than 3 (e.g., no more than 2.8, such as no        more than 2.6), and/or between 2 and 3 (e.g., between 2.2 and        2.8, such as between 2.4 and 2.6), e.g., 2.5, times the wire        diameter D_(W),    -   an outer coil diameter C₂ that equals between 90% and 110%        (e.g., 100%) of the outer coil diameter C₁ of        current-application longitudinal segment 62, and/or    -   an outer coil diameter C₂ of at least 3 (e.g., at least 4), no        more than 7 (e.g., no more than 6), and/or between 3 and 7        (e.g., between 4 and 6), e.g., 5, times the wire diameter D_(W).

Typically, providing the above-mentioned pitches enables the thoroughapplication of insulation to electrically-insulated lead longitudinalsegment 64, particularly if a vapor deposition process is used to applythe insulation (e.g., parylene). In addition, lead longitudinal segment64 may have a greater pitch than current-application longitudinalsegment 62 in part because lead longitudinal segment 64 generally doesnot require as much flexibility as current-application longitudinalsegment 62.

For other applications, lead longitudinal segment 64 is not coiled, inthe absence of any applied forces; for example, lead longitudinalsegment 64 may be straight or zigzag-shaped (configurations not shown).

For some applications, wire 60 further includes an intermediatelongitudinal segment 70, which (a) is longitudinally betweencurrent-application longitudinal segment 62 and lead longitudinalsegment 64, (b) typically has an entire longitudinal length L₃ of atleast 1 mm (e.g., at least 2 mm), no more than 6 mm (e.g., no more than4 mm), and/or between 1 and 6 mm (e.g., between 2 and 4 mm), in theabsence of any applied forces, and (c) in the absence of any appliedforces, either (i) is coiled, and has a mean pitch P₃ greater than outercoil diameter C₁ of current-application longitudinal segment 62, asshown in FIG. 2, or (ii) is not coiled, as shown in FIGS. 3A-B. (As usedin the present application, including the claims, when a segment isdescribed as “longitudinally between” two other segments, the segment isnot necessarily adjacent to the two other segments. In other words,additional segments, which may or may not be mentioned, maylongitudinally intervene between the segment and one or both of the twoother segments.)

For some applications, intermediate longitudinal segment 70 iselectrically insulated along at least a longitudinal portion ofintermediate longitudinal segment 70.

For some applications in which intermediate longitudinal segment 70 iscoiled, intermediate longitudinal segment 70 has one or more of thefollowing dimensions, in the absence of any applied forces:

-   -   a mean pitch P₃ of at least 125%, no more than 250%, and/or        between 125% and 250% of the outer coil diameter C₁ of        current-application longitudinal segment 62,    -   a mean pitch P₃ of at least 5 (e.g., at least 6, such as at        least 9), no more than 20 (e.g., no more than 13, such as no        more than 11), and/or between 5 and 20 (e.g., between 6 and 13,        such as between 9 and 11), e.g., 10, times the wire diameter        D_(W),    -   a mean pitch P₃ that equals (a) at least mean pitch P₁ of        current-application longitudinal segment 62, and (b) no more        than mean pitch P₂ of lead longitudinal segment 64,    -   an outer coil diameter C₃ equal to between 90% and 110% (e.g.,        100%) of the outer coil diameter C₁ of current-application        longitudinal segment 62, and/or    -   an outer coil diameter C₃ of at least 3 (e.g., at least 4), no        more than 7 (e.g., no more than 6), and/or between 3 and 7        (e.g., between 4 and 6) times the wire diameter D_(W).

Reference is now made to FIG. 3A, which is a schematic illustration ofanother configuration of electrode 22, in accordance with an applicationof the present invention. This configuration is the same as theconfiguration described hereinabove with reference to FIG. 2, exceptthat intermediate longitudinal segment 70 is not coiled, in the absenceof any applied forces.

For some applications, wire 60 further includes a partiallynon-electrically-insulated pin-connector longitudinal segment 72. Leadlongitudinal segment 64 is longitudinally between current-applicationlongitudinal segment 62 and pin-connector longitudinal segment 72. Forthese applications, intervertebral-disc-treatment system 20 typicallycomprises an electrode assembly 74, which comprises electrode 22 and apin 76, which is mechanically fixed to and in electrical communicationwith pin-connector longitudinal segment 72. Pin 76 and pin-connectorlongitudinal segment 72 are permanently connected, typically by welding(e.g., laser or spot welding).

For some applications, such as shown, pin-connector longitudinal segment72 is coaxial with a central longitudinal axis 80 ofelectrically-insulated lead longitudinal segment 64, in the absence ofany applied forces.

For some applications, such as shown in FIGS. 2 and 3A, pin-connectorlongitudinal segment 72 is coiled, in the absence of any applied forces.For some of these applications, such as shown in FIGS. 2 and 3A, coiledpin-connector longitudinal segment 72 is welded to the outside of pin76.

For some applications, pin-connector longitudinal segment 72 has one ormore of the following dimensions, in the absence of any applied forces:

-   -   a mean pitch P₄ that equals at least 125%, no more than 250%,        and/or between 125% and 250% of the outer coil diameter C₂ of        current-application longitudinal segment 62,    -   a mean pitch P₄ of at least 5, no more than 20 (e.g., no more        than 10, such as no more than 7), and/or between 5 and 20 (e.g.,        between 5 and 10, such as between 3 and 7 times), e.g., 7, times        the wire diameter D_(W),    -   an outer coil diameter C₄ that equals between 90% and 110%        (e.g., 100%) of the outer coil diameter C₂ of        current-application longitudinal segment 62.    -   an outer coil diameter C₄ of at least 3 (e.g., at least 4), no        more than 7 (e.g., no more than 6), and/or between 3 and 7        (e.g., between 4 and 6), e.g., 5, times the wire diameter D_(W),        and/or    -   an entire longitudinal length L₄ of between 1 and 4 mm.

Reference is now made to FIG. 3B, which is a schematic illustration ofyet another configuration of electrode 22, in accordance with anapplication of the present invention. In this configuration, pin 76 isshaped as a tube 77 that defines a lumen. An end portion 78 ofpin-connector longitudinal segment 72 may be a straight section locatedalong the axis of pin-connector longitudinal segment 72. For example,the connection may be fixated by crimping the tube of pin 76 on the wireof pin-connector longitudinal segment 72. The coating (e.g., parylenecoating) covers this section as well. Typically, the only part of pin 76that is not be coated is the proximal end thereof, which serves as anelectrical connector pin (by being insertable into a female electricalconnector, typically after the electrode has been implanted). Theelectrical path is thus electrically connected to the control circuitry50 and insulated from the body. For some applications, a seal 82 (e.g.,comprising silicone) is provided that surrounds the connector/pininterface with electrode lead 52 to control circuitry 50. Optionally,seal 82 is shaped so as to define wings 84, which may be used to anchorthe system.

For some applications, one or more of current-application longitudinalsegment 62, lead longitudinal segment 64, intermediate longitudinalsegment 70, and pin-connector longitudinal segment 72 has an inner coildiameter of at least 0.25 (e.g., at least 0.27), no more than 0.36(e.g., no more than 0.33), and/or between 0.25 and 0.36 (e.g., between0.27 and 0.33), e.g., 0.6, times the respective outer coil diameter ofthe segment, in the absence of any applied forces.

Typically, wire 60 has the same diameter D_(W) along all ofcurrent-application longitudinal segment 62, lead longitudinal segment64, intermediate longitudinal segment 70, and pin-connector longitudinalsegment 72. Alternatively, diameter D_(W) varies between one or more ofcurrent-application longitudinal segment 62, lead longitudinal segment64, intermediate longitudinal segment 70, and/or pin-connectorlongitudinal segment 72.

For some applications, the coil of one or more longitudinal segments ofelectrode 22 is filled with a pharmaceutical, such as an antibioticpharmaceutical, an anti-inflammation pharmaceutical, or an analgesicpharmaceutical.

Reference is now made to FIG. 4, which is a schematic illustration of a3-mm long portion 90 of current-application longitudinal segment 62, inaccordance with an application of the present invention. Thisconfiguration is applicable to the configurations of electrode 22 ofFIGS. 2, 3, and/or 5. For some applications, when a central longitudinalaxis 92 of 3-mm long portion 90 (measured along central longitudinalaxis 92 when the portion is straight, in the absence of any appliedforces) of current-application longitudinal segment 62 is curved in aplane only until all adjacent turns 94 of coiled wire 60 of portion 90touch one another, central longitudinal axis 92 of the portion has aradius of curvature R_(C) of at least 5 mm, no more than 10 mm, and/orbetween 5 and 10 mm.

Such a radius of curvature provides current-application longitudinalsegment 62 with the flexibility to curve and flex. If, on the one hand,adjacent turns 94 of coiled wire 60 instead touched one other in theabsence of any applied forces, current-application longitudinal segment62 would not have such flexibility to curve. If, on the other hand, meanpitch P₁ of current-application longitudinal segment 62 weresubstantially larger, current-application longitudinal segment 62 mightbe too stiff.

For some applications, lead longitudinal segment 64 has the curvatureparameters described hereinabove with reference to FIG. 4.

Reference is now made to FIG. 5, which is a schematic illustration ofanother configuration of electrode 22, in accordance with an applicationof the present invention. In this configuration, electrode 22 furthercomprises a water-permeable element 96 that runs along at least alongitudinal portion 98 of intermediate longitudinal segment 70, therebyenhancing fluid flow through annulus fibrosus 46 caused by theapplication of the voltage, to a level greater than possible throughother portions of annulus fibrosus 46. For some applications,water-permeable element 96 comprises a membrane. Alternatively oradditionally, for some applications, water-permeable element 96comprises an acid selected from the group consisting of: glycolic acidand lactic acid. For some applications, water-permeable element 96 ispre-attached to longitudinal portion 98. Alternatively, water-permeableelement 96 may be placed separately into the bore through annulusfibrosus 46.

For some of these applications, intermediate longitudinal segment 70 iscoiled, in the absence of any applied forces, such as describedhereinabove with reference to FIG. 2, and water-permeable element 96 isdisposed within the channel defined by the coil. Alternatively oradditionally, intermediate longitudinal segment 70 is partially orentirely embedded in intermediate longitudinal segment 70.

Reference is again made to FIG. 1. At least a portion of electrode 22 isimplanted in a body of a subject, typically such that:

-   -   current-application longitudinal segment 62 is disposed at least        partially in intervertebral disc 30 of the subject, typically        entirely in intervertebral disc 30 (either entirely in nucleus        pulposus 42 of intervertebral disc 30, or partially in a nucleus        pulposus of intervertebral disc 30 and partially in annulus        fibrosus 46 of intervertebral disc 30, as shown in FIG. 1),    -   at least a portion of lead longitudinal segment 64 is disposed        in the body of the subject outside intervertebral disc 30, and    -   if provided, intermediate longitudinal segment 70 is disposed at        least in part in annulus fibrosus 46 of intervertebral disc 30;        providing the relatively large pitch for intermediate        longitudinal segment 70, or not coiling intermediate        longitudinal segment 70 (as described hereinabove with reference        to FIG. 3), may reduce the likelihood that the portion of        intermediate longitudinal segment 70 that is within annulus        fibrosus 46 forms a tunnel, which might cause leakage of fluid        from nucleus pulposus 42.

Reference is now made to FIG. 6, which is a flow chart illustrating amethod 100 of manufacturing electrode 22, in accordance with anapplication of the present invention, and to FIG. 7, which is aschematic illustration of a polymer boot 102 used in manufacturingmethod 100, in accordance with an application of the present invention.Manufacturing method 100 may be used to manufacture the configurationsof electrode 22 of FIGS. 2, 3, and/or 5. Manufacturing method 100 beginsat an electrode provision step 110 by providing electrode 22, in any ofthe configurations described hereinabove that include intermediatelongitudinal segment 70, before electrically-insulated lead longitudinalsegment 64 has been coated with an electrically-insulating coating. Asmentioned above, intermediate longitudinal segment 70, in the absence ofany applied forces, either (a) is coiled and has a mean pitch P₃ that isgreater than an outer coil diameter C₁ of current-applicationlongitudinal segment 62 or (b) is not coiled.

At a polymer boot provision step 112, polymer boot 102 is provided; forsome applications, polymer boot 102 comprises a silicone boot. Polymerboot 102 is shaped so as to define an enclosed space 116 with an opening118 having a perimeter.

At masking step 120, a portion 126 of electrode 22 is masked by placingboot 102 on portion 126 of electrode 22, such that:

-   -   current-application longitudinal segment 62 is within enclosed        space 116,    -   lead longitudinal segment 64 is outside boot 102, and    -   intermediate longitudinal segment 70 passes through opening 118        such that the perimeter of opening 118 forms a tight seal with        at least a portion of intermediate longitudinal segment 70.

At a vapor deposition chamber step 130, boot 102 and electrode 22 areplaced into a vapor deposition chamber 134 (which is illustrated highlyschematically in FIG. 7). At a parylene coating step 140, a parylenecoating (or another biocompatible non-conducting material known in theart) is applied to lead longitudinal segment 64 by vapor depositionwithin deposition chamber 134, as is known in the vapor deposition art.Boot 102 and electrode 22 are removed from vapor deposition chamber 134,and boot 102 is removed from electrode 22.

This masking technique, in combination with the geometry of electrode22, solves the problem of how to tightly mask current-applicationlongitudinal segment 62 during vapor deposition ofelectrically-insulating parylene onto lead longitudinal segment 64. Theperimeter of opening 118 of boot 102, when applied to thehigh-coil-pitch, or coil-lacking, intermediate longitudinal segment 70,tightly squeezes the intermediate longitudinal segment, therebypreventing gaseous leakage of the parylene into the boot and ontocurrent-application longitudinal segment 62. Such tight squeezing wouldnot be possible if intermediate longitudinal segment 70 were moretightly coiled (i.e., had a lower coil pitch).

Reference is now made to FIG. 8, which is schematic illustrations of animplantation system 200 for implanting at least a portion of electrode22 in a body of a subject, in accordance with an application of thepresent invention. Implantation system 200 may be used to implant theconfigurations of electrode 22 of FIGS. 2, 3, and/or 5. Implantationsystem 200 comprises the following components, each of which isdescribed in detail hereinbelow:

-   -   a hollow insertion needle 210, which, at a proximal end thereof,        is axially fixed to a needle-connection fitting 212; insertion        needle 210 is used for inserting electrode 22 partially into        intervertebral disc 30, as described hereinbelow with reference        to FIGS. 11A-B; typically, insertion needle 210 has a length of        between 60 and 120 mm, such as between 80 and 100 mm, e.g., 90        mm;    -   a spacer 216, which defines a channel therethrough for insertion        of insertion needle 210 from a proximal side 218 of spacer 216        to a distal side 220 of spacer 216, until needle-connection        fitting 212 abuts proximal side 218 of spacer 216; spacer 216        serves to limit a depth of penetration of insertion needle 210,        as described hereinbelow with reference to FIGS. 11A-B;    -   an electrode loader 224, which is used to advance electrode 22        into insertion needle 210, as described hereinbelow with        reference to FIGS. 13A-15B; and    -   a needle-withdrawal handle 228, which is used to withdrawn        insertion needle 210 from disc 30 after delivery of electrode 22        into the disc, as described hereinbelow with reference to FIGS.        16A-18C.

For some applications, one or more (e.g., all) of the components ofimplantation system 200 are provided as a kit, typically in sterilepackaging 202. The components of implantation system 200 may be providedin various stages of assembly, depending on packaging needs and otherfactors. Typically, electrode 22 is also provided in the kit, such as inthe same sterile packaging 202 as the components of implantation system200.

Reference is now made to FIGS. 9A-B, which are schematic illustrationsof several components of implantation system 200, in accordance with anapplication of the present invention. FIG. 9A shows needle-withdrawalhandle 228 attached to spacer 216, while insertion needle 210 passesthrough the channel of spacer 216. FIG. 9A also shows needle-connectionfitting 212 fixed to insertion needle 210 and disposed withinneedle-withdrawal handle 228. FIG. 9B shows the relationship of theabove-mentioned components.

Reference is now made to FIG. 10, which is a flow chart illustrating amethod 240 of implanting at least a portion of electrode 22 in a body ofa subject, in accordance with an application of the present invention,and FIGS. 11A-20, which are schematic illustrations of steps ofimplantation method 240, in accordance with an application of thepresent invention. Implantation method 240 may be used to implant theconfigurations of electrode 22 of FIGS. 2, 3, and/or 5. Implantationmethod 240 uses implantation system 200, described hereinabove withreference to FIGS. 8 and 9A-B.

FIGS. 11A-B are schematic illustrations of a needle insertion step 242of implantation method 240, in accordance with an application of thepresent invention. Before inserting insertion needle 210 intointervertebral disc 30, insertion needle 210 (which is axially fixed toa needle-connection fitting 212) is inserted through spacer 216. Forexample, needle-connection fitting 212 may be female, in which caseneedle-connection fitting 212 typically comprises a female Luer taper.Spacer 216 serves to limit a depth penetration of insertion needle 210,so that the insertion needle does not penetrate the far side of annulusfibrosus 46 of disc 30. Optionally, a length of spacer 216 isadjustable, or a set of spacers 216 having different respective lengthsis provided, in order to accommodate discs 30 of different sizes.

Also before inserting insertion needle 210 into intervertebral disc 30,an anti-coring stylet 244 is inserted through needle-connection fitting212 and spacer 216 and into insertion needle 210, with the distal end ofanti-coring stylet 244 advanced to the distal end of insertion needle210. For some applications, anti-coring stylet 244 has a beveled distalend 246 that conforms to the beveled distal end of insertion needle 210.

At needle insertion step 242, insertion needle 210 (with anti-coringstylet 244 therein) is partially inserted into disc 30, until spacer 216contacts an external surface of annulus fibrosus 46. After insertion,the distal end of insertion needle 210 (and the distal end ofanti-coring stylet 244) typically is near, but does not penetrate, thefar side of annulus fibrosus 46. Alternatively, the distal end ofinsertion needle 210 (and the distal end of anti-coring stylet 244) isinserted into the far side of annulus fibrosus 46, e.g., to ultimatelyallow electrode 22 serve as an anchor. For some applications, the angleof penetration of the insertion needle is about 30 degrees.

FIG. 12 is a schematic illustration of an anti-coring stylet 244retraction step 248 of implantation method 240, in accordance with anapplication of the present invention. At anti-coring stylet 244retraction step 248, anti-coring stylet 244 is retracted, leavinginsertion needle 210 in disc 30, and spacer 216 contacting the externalsurface of annulus fibrosus 46.

FIGS. 13A-C are schematic illustrations of an electrode loader alignmentstep 252 of implantation method 240, in accordance with an applicationof the present invention. Electrode loader 224 comprises anelectrode-loader connection fitting 254, which, for example, may bemale, in which case electrode-loader connection fitting 254 typicallycomprises a male Luer taper, which is mounted near a distal end of ahollow loader needle 256. Typically, loader needle 256 has a length ofbetween 60 and 120 mm, such as between 80 and 100 mm, e.g., 90 mm.

Electrode 22 is loaded in loader needle 256, with a distal end ofelectrode 22 disposed near a distal end of loader needle 256. Electrodeloader 224 also comprises a loader stylet 258, which is loaded partiallywithin loader needle 256 and disposed such that a distal end of loaderstylet 258 abuts a proximal end of electrode 22 (typically a proximalend of pin 76 of electrode 22). Typically, loader stylet 258 is notbeveled at its distal end (i.e., it typically has a straight distalend). Loader stylet 258 is held in place by a connecting element 260,which may comprise a Luer connector, such that the distal end of loaderstylet 258 can push electrode 22 distally, as described hereinbelow withreference to FIGS. 15A-B. At electrode loader alignment step 252,electrode loader 224 is aligned with insertion needle 210.

FIGS. 14A-B are schematic illustrations of an electrode-loaderconnection step 264 of implantation method 240, in accordance with anapplication of the present invention. At electrode-loader connectionstep 264, electrode loader 224 is connected to insertion needle 210,such as by connecting electrode-loader connection fitting 254 toneedle-connection fitting 212, such as, for example, by way of rotation.As a result of this connection, a distal end of loader needle 256 abutsa proximal end of insertion needle 210.

FIGS. 15A-B are schematic illustrations of an electrode advancement step268 of implantation method 240, in accordance with an application of thepresent invention. At electrode advancement step 268, loader stylet 258is gently advanced distally within loader needle 256 and pusheselectrode 22 distally from loader needle 256 into insertion needle 210,which, as mentioned above, is disposed partially in disc 30. Forexample, electrode 22 may penetrate about 2 cm into disc 30.Electrode-loader connection fitting 254 is disconnected fromneedle-connection fitting 212, at an electrode-loader disconnection step272 (not shown), and electrode loader 224 is removed.

FIGS. 16A-C are schematic illustrations of a needle-withdrawal-handlealignment step 276 of implantation method 240, in accordance with anapplication of the present invention. Needle-withdrawal handle 228comprises a handle stylet 278, which is typically axially fixed withinthe needle-withdrawal handle. At needle-withdrawal-handle alignment step276, needle-withdrawal handle 228 and handle stylet 278 are aligned withinsertion needle 210 (and spacer 216).

FIGS. 17A-B are schematic illustrations of a needle-withdrawal-handleconnection step 282 of implantation method 240, in accordance with anapplication of the present invention. At needle-withdrawal-handleconnection step 282, needle-withdrawal handle 228 is connected toinsertion needle 210, such as by connecting needle-withdrawal handle 228to spacer 216 (such as by friction, snapping on, and/or rotation). Uponthe connection being made, needle-connection fitting 212 is disposedwithin needle-withdrawal handle 228, near a distal end of theneedle-withdrawal handle, and the distal end of handle stylet 278 isdisposed within needle-connection fitting 212 abutting the proximal endof electrode 22 (typically the proximal end of pin 76 of electrode 22).

FIGS. 18A-C are schematic illustrations of an insertion-needlewithdrawal step 286 of implantation method 240, in accordance with anapplication of the present invention. At insertion-needle withdrawalstep 286, needle-connection fitting 212 is withdrawn proximally withinneedle-withdrawal handle 228, while needle-withdrawal handle 228 is heldstationary. As mentioned above with reference to FIGS. 11A-B, insertionneedle 210 is axially fixed to needle-connection fitting 212. As aresult, needle-connection fitting 212, as it is proximally withdrawn,withdraws insertion needle 210 from disc 30 (insertion needle 210 isslidable with respect to spacer 216). Handle stylet 278, which isaxially fixed with respect to needle-withdrawal handle 228 and abuts theproximal end of electrode 22, prevents proximal motion of electrode 22.As a result, electrode 22 remains generally axially stationary,partially inserted in disc 30.

FIG. 19 is a schematic illustration of a needle-withdrawal-handlewithdrawal step 290 of implantation method 240, in accordance with anapplication of the present invention. At needle-withdrawal-handlewithdrawal step 290, needle-withdrawal handle 228, with spacer 216 stillattached thereto, is gently withdrawn proximally, thereby releasingelectrode 22 and leaving electrode 22 implanted partially in disc 30 andpartially in the body of the subject outside the disc.

FIG. 20 is a schematic illustration of electrode 22 implanted partiallyin disc 30 and partially in the body of the subject outside the disc, inaccordance with an application of the present invention. For example,about 2 cm of electrode 22 may be disposed in disc 30, and the remainder(e.g., about 5 to 6 cm) may be disposed outside the disc.

Reference is again made to FIG. 1. In some applications of the presentinvention, intervertebral-disc-treatment system 20 comprises:

-   -   at least one intra-pulposus exposed electrode surface 280 (which        is electrically conductive), which is configured to be implanted        in nucleus pulposus 42 of intervertebral disc 30;    -   a plurality of extra-pulposus exposed electrode surfaces 44        (e.g., at least 3, no more than 10, and/or between 3 and 10,        such as exactly 3), which are configured to be implanted outside        nucleus pulposus 42, in electrical communication with        intervertebral disc 30; and    -   control circuitry 50, which is (a) electrically coupled to the        at least one intra-pulposus exposed electrode surface 280 and        the plurality of extra-pulposus exposed electrode surfaces        44, (b) configured to separately control at least two of the        plurality of extra-pulposus exposed electrode surfaces 44; for        example, control circuitry 50 may be electrically coupled to the        extra-pulposus exposed electrode surfaces separately via        separate electrical conductors.

Providing the plurality of separately-controllable extra-pulposusexposed electrode surfaces 44 distributes the generation of hydrogen,thereby reducing any local build-up of hydrogen at any single electrodesurface.

For some applications, control circuitry 50 is configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface 280 to be        a cathode, and one or more of the plurality of extra-pulposus        exposed electrode surfaces 44 to be one or more respective        anodes, and (b) electroosmotically drive fluid into nucleus        pulposus 42 to increase pressure in intervertebral disc 30, by        applying a first mean voltage of less than 1.23 V (sometimes        known in the art as the “electrolysis voltage”) (e.g., less than        1 V, such as less than 500 mV, e.g., less than 300 mV) between        the at least one intra-pulposus exposed electrode surface 280        and the one or more of the plurality of extra-pulposus exposed        electrode surfaces 44, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface 280 to be an        anode, and the plurality of extra-pulposus exposed electrode        surfaces 44 to be a respective plurality of cathodes, and (b)        generate oxygen within nucleus pulposus 42 by electrolysis, by        applying a second mean voltage of at least 1.23 V (e.g., at        least 1.5 V, such as at least 2 V) between the at least one        intra-pulposus exposed electrode surface 280 and the plurality        of extra-pulposus exposed electrode surfaces 44.

The increase in fluid in nucleus pulposus 42 during thepressure-increasing mode of operation generally treats or preventsfurther degeneration of the disc caused at least in part by loss offluid. The applied current may also help introduce nutritionalsubstances into the disc. The generation of oxygen within nucleuspulposus 42 during the oxygen-generating mode generally treats hypoxia,which, if untreated, sometimes causes disc degeneration. The generationof oxygen may also improve glucose metabolism, while reducing lacticacid generation.

For some applications, control circuitry 50 is configured to applydirect current, e.g., with an average amplitude of between 1 and 5 mA.For some applications, the control unit is configured to apply thedirect current as a series of pulses. For some applications, the controlunit is configured to apply the direct current as the series of pulseswith a duty cycle of between 1% and 50%.

Typically, control circuitry 50 is not configured to actively balancethe applied positive and negative charges. Rather, control circuitry 50is configured to allow the passive balancing of the applied positive andnegative charges.

Typically, control circuitry 50 is configured to separately control allof the plurality of extra-pulposus exposed electrode surfaces 44; forexample, control circuitry 50 may be electrically coupled to theextra-pulposus exposed electrode surfaces separately via separateelectrical conductors.

For some applications, as shown in FIG. 1, the at least oneintra-pulposus exposed electrode surface 280 comprisesnon-electrically-insulated current-application longitudinal segment 62of electrode 22, described hereinabove. Alternatively, the at least oneintra-pulposus exposed electrode surface 280 does not comprisenon-electrically-insulated current-application longitudinal segment 62of electrode 22; instead, another electrode is provided; for example,electrodes may be used that are described in U.S. Pat. No. 8,577,469and/or U.S. application Ser. No. 14/982,187, filed Dec. 29, 2015, whichpublished as US Patent Application Publication 2017/0182317, both ofwhich are assigned to the assignee of the present application andincorporated herein by reference, and are optionally implanted during aconventional surgical procedure to repair disc 30 and/or nucleuspulposus 42, including a standard approach for inserting a needle indisc 30. Alternatively, an electrode known in the art is used.

For some applications, control circuitry 50 is configured, during aperiod of time, to assume (a) the pressure-increasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% (e.g., less than 5%, such as lessthan 1%) of the aggregate first duration. By way of example and notlimitation, control circuitry 50 may assume the oxygen-generating modeof operation for 1-30 seconds (e.g., 1-30 seconds every hour), andassume the pressure-increasing mode of operation at other times.Although control circuitry 50, when in the oxygen-generating mode ofoperation, may electroosmotically drive fluid out of nucleus pulposus 42and thus decrease pressure in intervertebral disc 30, because theaggregate second duration is so much less than the aggregate firstduration, the aggregate effect of the application of voltages is anincrease in pressure in intervertebral disc 30.

For some applications, control circuitry 50 is configured to, in theoxygen-generating mode of operation, generate oxygen within nucleuspulposus 42 by electrolysis, by applying the second mean voltage betweenthe at least one intra-pulposus exposed electrode surface 280 andrespective different subsets of the plurality of extra-pulposus exposedelectrode surfaces 44 at respective different times. For someapplications, each of the subsets consists of exactly one of theplurality of extra-pulposus exposed electrode surfaces 44. Activatingextra-pulposus exposed electrode surfaces 44 at different times furtherdistributes the generation of hydrogen, thereby further reducing anylocal build-up of hydrogen at any single electrode surface.

For some applications, intervertebral-disc-treatment system 20 furthercomprises a sensor, which is configured to sense a parameter indicativeof a quantity of the oxygen generated by the electrolysis. Controlcircuitry 50 is configured to modulate the oxygen-generating mode ofoperation responsively to the sensed parameter. For some applications,control circuitry 50 is configured to modulate the oxygen-generatingmode of operation by modulating a duration of one or more occurrences ofthe oxygen-generating mode of operation. Alternatively or additionally,control circuitry 50 is configured to modulate the oxygen-generatingmode of operation by modulating an electrical parameter of the secondmean voltage (e.g., the voltage, amplitude, duty cycle, and/orfrequency). For some applications, the sensed parameter is an oxygenconcentration in nucleus pulposus 42 and/or a pH in nucleus pulposus 42.The sensor may be provided in the application of the present inventiondescribed immediately hereinbelow with reference to FIGS. 1 and 21.

Reference is still made to FIG. 1, and is additionally made to FIG. 21,which is a schematic illustration of another configuration ofintervertebral-disc-treatment system 20, in accordance with anapplication of the present invention. In some applications of thepresent invention, intervertebral-disc-treatment system 20 comprises:

-   -   at least one intra-pulposus exposed electrode surface 280, which        is configured to be implanted in nucleus pulposus 42 of        intervertebral disc 30;    -   one or more extra-pulposus exposed electrode surfaces 44,        which (a) are configured to be implanted outside nucleus        pulposus 42, in electrical communication with intervertebral        disc 30, and (b) have an aggregate electrically-exposed surface        area of at least 3 cm2, such as at least 4 cm2, e.g., at least 5        cm2; and    -   control circuitry 50, which is electrically coupled to the at        least one intra-pulposus exposed electrode surface 280 and one        or more extra-pulposus exposed electrode surfaces 44.

For some applications, control circuitry 50 is configured to:

-   -   repeatedly assume a pressure-increasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in the pressure-increasing mode of operation, (a) configure the        at least one intra-pulposus exposed electrode surface 280 to be        a cathode, and the one or more extra-pulposus exposed electrode        surfaces 44 to be one or more respective anodes, and (b)        electroosmotically drive fluid into nucleus pulposus 42 to        increase pressure in intervertebral disc 30, by applying a first        mean voltage of less than 1.23 V (e.g., less than 1 V, such as        less than 500 mV, e.g., less than 300 mV) between the at least        one intra-pulposus exposed electrode surface 280 and the one or        more extra-pulposus exposed electrode surfaces 44, and    -   in the oxygen-generating mode of operation, (a) configure the at        least one intra-pulposus exposed electrode surface 280 to be an        anode, and the one or more extra-pulposus exposed electrode        surfaces 44 to be a respective plurality of cathodes, and (b)        generate oxygen within nucleus pulposus 42 by electrolysis, by        applying a second mean voltage of at least 1.23 V (e.g., at        least 2 V) between the at least one intra-pulposus exposed        electrode surface 280 and the one or more extra-pulposus exposed        electrode surfaces 44.

The increase in fluid in nucleus pulposus 42 during thepressure-increasing mode of operation generally treats or preventsfurther degeneration of the disc caused at least in part by loss offluid. The applied current may also help introduce nutritionalsubstances into the disc. The generation of oxygen within nucleuspulposus 42 during the oxygen-generating mode generally treats hypoxia,which, if untreated, sometimes causes disc degeneration. The generationof oxygen may also improve glucose metabolism, while reducing lacticacid generation. Providing the relatively large aggregateelectrically-exposed surface area of at least 3 cm2 distributes thegeneration of hydrogen, thereby reducing any local build-up of hydrogenat the electrode-tissue interface.

For some applications, such as shown in FIG. 21,intervertebral-disc-treatment system 20 comprises exactly oneextra-pulposus exposed electrode surface 44 having anelectrically-exposed surface area of at least 3 cm2. Alternatively, anexternal surface of a can of control circuitry 50 serves asextra-pulposus exposed electrode surface 44 (configuration not shown).For other applications, such as shown in FIG. 1,intervertebral-disc-treatment system 20 comprises a plurality ofextra-pulposus exposed electrode surfaces 44.

For some applications, control circuitry 50 is configured to applydirect current, e.g., with an average amplitude of between 1 and 5 mA.For some applications, the control unit is configured to apply thedirect current as a series of pulses. For some applications, the controlunit is configured to apply the direct current as the series of pulseswith a duty cycle of between 1% and 50%.

For some applications, control circuitry 50 is configured, during aperiod of time, to assume (a) the pressure-increasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% (e.g., less than 5%, such as lessthan 1%) of the aggregate first duration. By way of example and notlimitation, control circuitry 50 may assume the oxygen-generating modeof operation for a few seconds every hour, and assume thepressure-increasing mode of operation at other times. Although controlcircuitry 50, when in the oxygen-generating mode of operation, mayelectroosmotically drive fluid out of nucleus pulposus 42 and thusdecrease pressure in intervertebral disc 30, because the aggregatesecond duration is so much less than the aggregate first duration, theaggregate effect of the application of voltages is an increase inpressure in intervertebral disc 30.

Reference is again made to FIGS. 1 and 21. For some applications,control circuitry 50 is configured to drive intra-pulposus exposedelectrode surface 280 and the one or more extra-pulposus exposedelectrode surfaces 44 to electroosmotically drive fluid between insideand outside nucleus pulposus 42 based on a circadian cycle of thesubject. For some applications, a housing containing control circuitry50 is injectable, with an anchor at the proximal end. One or moreextra-pulposus exposed electrode surfaces 44 are fixed to an externalsurface of the housing. For example, the housing may be implantedimmediately posterior to the spinal column. For some applications,control circuitry 50 is configured to be implanted subcutaneously, ifthe housing containing the control circuitry is small. Alternatively,for some applications, control circuitry 50 is configured to beimplanted or elsewhere in the subject's body, if the housing of thecontrol circuitry is larger (e.g., includes batteries).

For some applications, control circuitry 50 is driven by an externalcontroller that is in wireless or wired communication with controlcircuitry 50. For some applications, the external controller is mountedon a bed of the subject (e.g., disposed within a mattress), and isconfigured to activate control circuitry 50 only at night, and/or onlywhen the subject is sleeping. Such nighttime activation may coincidewith and support the filling phase of the disc, and thus be therapeuticeven though the patient experiences more pain during the day.Alternatively or additionally, control circuitry 50 is activated duringthe daytime, i.e., over the course of the day, because the pressure ishigher in the disc during application of vertical and mechanical load onthe disc, which causes the disc to lose fluid; the activation may thisreduce maximum damage to the disc. Further alternatively, the controlcircuitry is activated generally constantly or regularly intermittently(e.g., one hour on/one hour off). For some applications, controlcircuitry 50 is activated during rest of the subject, rather than duringactivity; for example, an accelerometer may be provided to identifymovement vs. rest of the subject.

For some applications, control circuitry 50 is configured to provide thesubject with control of activation of control circuitry 50, e.g., inresponse to activity or pain.

For example, the control may be provided from the subject's telephone(e.g., smartphone) or other electronic device.

For some applications, the method further comprises replacing nucleuspulposus 42 with an artificial substitute material before implantingintra-pulposus exposed electrode surface 280.

A first experiment was conducted on behalf of the inventors to study thefeasibility of using some of the techniques described hereinabove withreference to FIG. 1 to hydrate and dehydrate a spinal disc, and theimpact of the voltage application on the disc mass. The experimentevaluated three electrical protocols: (a) negative voltage inside thenucleus pulposus of the disc vs. outside the disc, (b) positive voltageinside the nucleus pulposus of the disc vs. outside the disc, and (c)control (no voltage applied to the nucleus pulposus of the disc). It wasfound that application of a negative voltage inside the nucleus pulposusof the disc enhanced the hydration of the disc, as compared to apositive voltage or no voltage. No dehydration effect was observed withapplication of a positive voltage to the nucleus pulposus.

The experiment used a total of six fresh bovine tail discs. In order toachieve equilibrium, the discs were placed in a saline solution for aperiod of one hour prior to application of the voltages. The discs werethen weighed. The discs were randomly assigned to the experimentalgroups as follows: (a) two specimens—negative voltage inside the nucleuspulposus of the disc vs. outside the disc, (b) two specimens—positivevoltage inside the nucleus pulposus of the disc vs. outside the disc,and (c) two specimens—control (no voltage applied to the nucleuspulposus of the disc).

The discs were placed inside a vessel and fully submerged in salinesolution. One electrode was inserted in the approximate center of thenucleus pulposus of each of the discs in experimental groups (a) and(b). The electrode was electrically-insulated except at its tip, and wasdesigned to allow submersion in liquid. The electrode was insertedlaterally (i.e., through the annulus of the disc). A second, ringelectrode was placed within the saline solution surrounding the disc.

Voltages of (a) −1 V and (b)+1 V were applied between the electrodes inthe two experimental groups (a) and (b), respectively. These voltageswere selected to be lower than the electrolysis voltage of water ofabout 1.2 V. After a period of two hours, the discs were removed andweighed again.

As set forth in Table 1 below, all of the discs increased in mass duringthe voltage-application period. The mass of the discs to which thenegative internal voltage was applied increased by 4.7% and 5.5%, whilethe mass of the other discs (positive internal voltage and control)increased by between 2.0% and 2.6%.

The inventors hypothesize that all of the discs absorbed liquid, whilethe application of the negative internal voltage contributed to anadditional absorption of 2-3%. The application of the positive internalvoltage did not result in dehydration of the disc.

TABLE 1 Mass after 1 Mass after 2 Mass Mass Disc hour immersion Voltagehours voltage change change # [g] (internal) application [g] [g] [%] 13.342 −1 V 3.527 0.185 5.5% 2 4.384 −1 V 4.590 0.206 4.7% 3 6.552 +1 V6.720 0.168 2.6% 4 4.558 +1 V 4.651 0.093 2.0% 5 7.346 0 7.531 0.1852.5% 6 6.074 0 6.209 0.135 2.2%

A second experiment was conducted on behalf of the inventors to studythe feasibility of using some of the techniques described hereinabovewith reference to FIG. 1 to hydrate a spinal disc and the impact of thevoltage application on the disc mass. The experiment evaluated twoelectrical protocols: (a) negative voltage inside the nucleus pulposusof the disc vs. outside the disc, and (b) control (no voltage applied tothe nucleus pulposus of the disc). It was found that application of anegative voltage inside the nucleus pulposus of the disc enhanced thehydration of the disc, as compared to no voltage. Higher voltagemarkedly increased the mass gain.

The experiment used a total of six fresh bovine tail discs. The discswere randomly assigned to the experimental groups as follows: (a) threespecimens—negative voltage inside the nucleus pulposus of the disc vs.outside the disc, and (b) three specimens—control (no voltage applied tothe nucleus pulposus of the disc).

The discs were weighed, and then placed inside a vessel and fullysubmerged in saline solution. One electrode was inserted in theapproximate center of the nucleus pulposus of each of the discs in theexperimental group (a). The electrode was electrically-insulated exceptat its tip, and was designed to allow submersion in liquid. Theelectrode was inserted laterally (i.e., through the annulus of thedisc). A second, ring electrode was placed within the saline solutionsurrounding the disc.

A voltage of −1 V was applied between the electrodes in the experimentalgroup (a). One hour after the beginning of application of the voltage, afirst pair of two of the discs (one negative voltage, one control) wereremoved and weighed. In the two remaining negative voltage discs, thevoltage was increased to −3 V.

Two hours after the beginning of application of the voltage, a secondpair of two of the discs (one negative voltage, one control) wereremoved and weighed.

Three hours after the beginning of application of the voltage, a thirdpair of two of the discs (one negative voltage, one control) wereremoved and weighed.

As set forth in Table 2 below, all of the discs increased in mass duringthe voltage-application period. In each pair, the disc to which thevoltage was applied increased in mass more than the control disc did.Increasing the voltage from −1 V to −3 V resulted in a markedlyincreased mass gain. It was noted, however, that the −3 V voltageapplication resulted in electrolysis of the solution, which was expectedsince the electrolysis threshold of water is about 1.2 V. Thiselectrolysis was observed as bubbles and discoloration in the solution.

The inventors hypothesize that all of the discs absorbed liquid, whilethe application of the negative internal voltage contributed to anadditional absorption.

TABLE 2 Duration of Mass Disc Starting mass Voltage voltage Endingchange # [g] (internal) application mass [g] [%] 1 6.047 −1 V 1 hour6.345  4.93% 2 6.227 0 1 hour 6.420  3.10% 3 5.988 −1 V, −3 V 2 hours6.605 10.30% 4 5.192 0 2 hours 5.444  4.85% 5 4.484 −1 V, −3 V 3 hours5.262 17.35% 6 4.236 0 3 hours 4.619  9.04%

The inventors hypothesize that application of −3 V, although possiblynot suitable for clinical use, served as a proxy for the effectivenessof longer-term voltage application at a lower voltage, such as −1 V.

As mentioned above, the discs were placed in a saline-dye solutionduring the experiment. The dye was methylene blue. After weighing thediscs, the discs were also dissected and inspected for dye penetration.In general, dye penetration was not observed in the discs.

Reference is now made to FIG. 22, which is a schematic illustration ofan eye-treatment system 300 for treating an eye 310 of a subject, inaccordance with an application of the present invention. Eye-treatmentsystem 300 is typically used for treating glaucoma. Eye-treatment system300 comprises:

-   -   a first exposed electrode surface 320, which is configured to be        implanted in a vitreous cavity 322 of eye 310;    -   a second exposed electrode surface 324, which is configured to        be implanted in a body of the subject at a site 326 outside        vitreous cavity 322; and    -   control circuitry 350, which is typically electrically coupled,        by one or more electrode leads 352, to first and second exposed        electrode surfaces 320 and 324.

For some applications, control circuitry 350 is configured to:

-   -   repeatedly assume a pressure-decreasing mode of operation in        alternation with an oxygen-generating mode of operation,    -   in both the pressure-decreasing mode of operation and the        oxygen-generating mode of operation, configure first exposed        electrode surface 320 to be an anode, and second exposed        electrode surface 324 to be a cathode,    -   in the pressure-decreasing mode of operation, electroosmotically        drive fluid from vitreous cavity 322 to outside vitreous cavity        322 to decrease pressure in vitreous cavity 322, by applying a        first mean voltage of less than 1.23 V (e.g., less than 1 V,        such as less than 500 mV, e.g., less than 300 mV) between first        and second exposed electrode surfaces 320 and 324, and    -   in the oxygen-generating mode of operation, generate oxygen        within vitreous cavity 322 by electrolysis, by applying a second        mean voltage of at least 1.23 V (e.g., at least 2 V) between        first and second exposed electrode surfaces 320 and 324.

The decrease in fluid in vitreous cavity 322 during thepressure-decreasing mode of operation generally treats glaucoma byreducing intraocular pressure. The generation of oxygen within vitreouscavity 322 during the oxygen-generating mode treats diabeticretinopathy, in which insufficient oxygen is naturally provided to theretina.

For some applications, site 326 is within a Schlemm's canal 354 of thesubject, and second exposed electrode surface 324 is configured to beimplanted within Schlemm's canal 354. In these applications, controlcircuitry 50 is configured to, in the pressure-decreasing mode ofoperation, electroosmotically drive the fluid from vitreous cavity 322to Schlemm's canal 354 to decrease the pressure in vitreous cavity 322,by applying the first mean voltage between first and second exposedelectrode surfaces 320 and 324.

For some applications, control circuitry 50 is configured, during aperiod of time, to assume (a) the pressure-decreasing mode of operationat least 10 times for an aggregate first duration and (b) theoxygen-generating mode of operation at least 10 times for an aggregatesecond duration that is less than 10% (e.g., less than 5%, such as lessthan 1%) of the aggregate first duration.

For some applications, control circuitry 50 is configured to applydirect current, e.g., with an average amplitude of between 1 and 5 mA.For some applications, the control unit is configured to apply thedirect current as a series of pulses. For some applications, the controlunit is configured to apply the direct current as the series of pulseswith a duty cycle of between 1% and 50%.

For some applications, eye-treatment system 300 further comprises asensor, which is configured to sense a parameter indicative of aquantity of the oxygen generated by the electrolysis. Control circuitry50 is configured to modulate the oxygen-generating mode of operationresponsively to the sensed parameter. For some applications, controlcircuitry 50 is configured to modulate the oxygen-generating mode ofoperation by modulating a duration of one or more occurrences of theoxygen-generating mode of operation. Alternatively or additionally,control circuitry 50 is configured to modulate the oxygen-generatingmode of operation by modulating an electrical parameter of the secondmean voltage (e.g., the voltage, amplitude, duty cycle, and/orfrequency). For some applications, the sensed parameter is an oxygenconcentration in vitreous cavity 322 and/or a pH in vitreous cavity 322.

For some applications, control circuitry 50 is configured to detect apressure difference between vitreous cavity 322 and outside vitreouscavity 322, and modulate the pressure-decreasing mode of operationresponsively to the pressure difference parameter in response to thedetected pressure difference.

Reference is now made to FIG. 23, which is a schematic illustration of adiabetic-retinopathy-treatment system 400 for treating diabeticretinopathy, in accordance with an application of the present invention.Diabetic-retinopathy-treatment system 400 comprises control circuitry420 and one or more electrodes 430 (e.g., at least 2, no more than 20,and/or between 2 and 20). The one or more electrodes 430 are configuredto be implanted penetrating a retina 440 of eye 310 (as shown), orplaced against an external surface of retina 440 (i.e., the surfacefacing into the interior of the eye) (configuration not shown).

Control circuitry 420 is configured to generate oxygen within retina 440by electrolysis, by (a) configuring the one or more electrodes 430 to beanodes, and (b) applying a mean voltage of at least 1.23 V (e.g., atleast 1.5 V, such as at least 2 V) between the one or more electrodes430 and one or more return cathodes 444 (e.g., anelectrically-conductive casing of control circuitry 420). The generatedoxygen treats diabetic retinopathy, which is characterized by damage toblood vessels in the retina, which reduces the oxygen supply to theretina.

For some applications, diabetic-retinopathy-treatment system 400comprises an antenna 446, which is configured to wirelessly receiveenergy for powering control circuitry 420. For example, antenna 446 mayhave an annular shape and be mounted around a lens 448 of the eye,either the natural lens or an intraocular lens (TOL) that is implantedto serve as a support for antenna 446. Alternatively, antenna 446 has adifferent structure and/or is implanted at a different site in the eyeor near the eye. Antenna 446 may be connected to control circuitry 420by one or more conductive wires 449.

Typically, electrodes 430 are implanted near a macula 442 of retina 440,most typically not on macula 442 itself, in order to avoid interferingwith the patient's vision. For example, as shown,diabetic-retinopathy-treatment system 400 may comprise a ring 450 thatis sized to be placed around macula 442, and electrodes 430 are fixed atdifferent respective sites along ring 450 around macula 442. Optionally,control circuitry 420 is also disposed along, or slightly outside, ring450.

In some applications of the present invention, the techniques andapparatus described herein are combined with techniques and apparatusdescribed in one or more of the following applications, which areassigned to the assignee of the present application and are incorporatedherein by reference:

-   -   U.S. Pat. No. 8,577,469 to Gross;    -   US Patent Application Publication 2014/0324128 to Gross; and    -   U.S. patent application Ser. No. 14/982,187, filed Dec. 29,        2015, which published as US Patent Application Publication        2017/0182317.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

The invention claimed is:
 1. Apparatus for treating an intervertebraldisc of a subject, the apparatus comprising: at least one intra-pulposusexposed electrode surface, which is configured to be implanted in anucleus pulposus of the intervertebral disc; one or more extra-pulposusexposed electrode surfaces, which are configured to be implanted outsidethe nucleus pulposus, in electrical communication with theintervertebral disc; and control circuitry, which is (a) electricallycoupled to the at least one intra-pulposus exposed electrode surface andone or more extra-pulposus exposed electrode surfaces, and (b)configured to drive fluid and introduce nutritional substances into theintervertebral disc, by applying a voltage between the at least oneintra-pulposus exposed electrode surface and the one or moreextra-pulposus exposed electrode surfaces.
 2. The apparatus according toclaim 1, wherein the control circuitry is configured to configure the atleast one intra-pulposus exposed electrode surface to be a cathode, andthe one or more extra-pulposus exposed electrode surfaces to be one ormore respective anodes.
 3. The apparatus according to claim 1, whereinthe control circuitry is additionally configured to drive the at leastone intra-pulposus exposed electrode surface and the one or moreextra-pulposus exposed electrode surfaces to improve glucose metabolismin the intervertebral disc.
 4. The apparatus according to claim 3,wherein the control circuitry is configured to improve the glucosemetabolism by driving the at least one intra-pulposus exposed electrodesurface and the one or more extra-pulposus exposed electrode surfaces togenerate oxygen within the nucleus pulposus by electrolysis.
 5. Theapparatus according to claim 3, wherein the control circuitry isconfigured to configure the at least one intra-pulposus exposedelectrode surface to be an anode, and the one or more extra-pulposusexposed electrode surfaces to be one or more respective cathodes.
 6. Theapparatus according to claim 1, wherein the control circuitry isadditionally configured to drive the at least one intra-pulposus exposedelectrode surface and the one or more extra-pulposus exposed electrodesurfaces to reduce lactic acid generation in the intervertebral disc. 7.The apparatus according to claim 6, wherein the control circuitry isconfigured to reduce the lactic acid generation by driving the at leastone intra-pulposus exposed electrode surface and the one or moreextra-pulposus exposed electrode surfaces to generate oxygen within thenucleus pulposus by electrolysis.
 8. The apparatus according to claim 6,wherein the control circuitry is configured to configure the at leastone intra-pulposus exposed electrode surface to be an anode, and the oneor more extra-pulposus exposed electrode surfaces to be one or morerespective cathodes.
 9. Apparatus for treating an intervertebral disc ofa subject, the apparatus comprising: at least one intra-pulposus exposedelectrode surface, which is configured to be implanted in a nucleuspulposus of the intervertebral disc; one or more extra-pulposus exposedelectrode surfaces, which are configured to be implanted outside thenucleus pulposus, in electrical communication with the intervertebraldisc; and control circuitry, which is (a) electrically coupled to the atleast one intra-pulposus exposed electrode surface and one or moreextra-pulposus exposed electrode surfaces, and (b) configured to improveglucose metabolism and reduce lactic acid generation in theintervertebral disc, by applying a voltage between the at least oneintra-pulposus exposed electrode surface and the one or moreextra-pulposus exposed electrode surfaces.
 10. The apparatus accordingto claim 9, wherein the control circuitry is configured to improve theglucose metabolism and reduce the lactic acid generation by driving theat least one intra-pulposus exposed electrode surface and the one ormore extra-pulposus exposed electrode surfaces to generate oxygen withinthe nucleus pulposus by electrolysis.
 11. The apparatus according toclaim 9, wherein the control circuitry is configured to configure the atleast one intra-pulposus exposed electrode surface to be an anode, andthe one or more extra-pulposus exposed electrode surfaces to be one ormore respective cathodes.